Construction of optical nodes using programmable roadms

ABSTRACT

Example embodiments of the present invention relate to programmable ROADMs used to construct optical nodes. Example embodiments include wavelength switches and waveguide switches, wherein the waveguide switches may be programmed to direct wavelength division multiplexed optical signals to and from the wavelength switches.

RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No. 15/497,380, filed Apr. 26, 2017, which is a continuation-in-part of U.S. application Ser. No. 15/160,171, filed May 20, 2016, now U.S. Pat. No. 9,667,374, which is a continuation of U.S. application Ser. No. 15/004,139, filed Jan. 22, 2016, now U.S. Pat. No. 9,374,186, which is a continuation of U.S. application Ser. No. 14/639,208, filed Mar. 5, 2015, now U.S. Pat. No. 9,276,695, which is a continuation of U.S. application Ser. No. 13/924,542, filed Jun. 22, 2013, now U.S. Pat. No. 9,008,514.

BACKGROUND

As the bandwidth needs of end customers increases, larger amounts of optical bandwidth will need to be manipulated closer to the end customers. A new breed of optical processing equipment will be needed to provide high levels of optical bandwidth manipulation at the lower cost points demanded at the networks closest to the end customers. This new breed of optical processing equipment will require new levels of optical signal processing integration.

SUMMARY

A method and corresponding apparatus in an example embodiment of the present invention relates to providing a means of manipulating optical signals at the lowest possible cost points. The example embodiment includes a compact light processing apparatus—utilizing wavelength equalizing arrays—whose level of equipment redundancy matches the economics associated with the location of the apparatus within provider networks.

According to an embodiment of the present invention, there is provided an optical node comprising of at least two optical degrees, a plurality of directionless add/drop ports, and at least one wavelength equalizing array; wherein the at least one wavelength equalizing array is used to both select wavelengths for each optical degree and to perform directionless steering for the plurality of directionless add/drop ports. According to another embodiment of the invention, an apparatus referred to as a ROADM circuit pack is described. The ROADM circuit pack is comprised of a least two optical degrees and a port common to the at least two optical degrees, wherein the common port is connectable to a plurality of directionless add/drop ports, and wherein wavelengths from the common port may be directed to any of the at least two degrees residing on the circuit pack. The ROADM circuit pack may additionally comprise of at least one wavelength equalizing array, wherein the at least one wavelength equalizing array is used to both select wavelengths for each degree, and to perform directionless steering of wavelengths to and from the plurality of directionless add/drop ports. The at least one equalizing array may further be utilized to aid in providing additional functionality to the ROADM circuit pack, including, but not limited to, a channel monitoring function and the functionality of at least one embedded transponder.

The invention also provides a method for constructing an optical node utilizing a wavelength equalizing array. The method comprises of allocating a first set of wavelength equalizers for selection of a first set of wavelengths for transmission from a first optical degree, and allocating at least a second set of wavelength equalizers for selection of at least a second set of wavelengths for transmission from at least a second optical degree; wherein the number of optical degrees comprising the node is used to determine the number of wavelength equalizers assigned to each set. The method further includes allocating an additional set of wavelength equalizers for selection of an additional set of wavelengths for transmission from a common port connectable to a plurality of directionless add/drop ports. The method may additionally include allocating wavelength equalizers for a channel monitoring function and for an embedded transponder function.

The present invention provides various advantages over conventional methods and apparatus for construction of optical nodes. The advantages arise from the use of a single wavelength equalizing array that allows for the construction of highly integrated optical nodes.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.

FIG. 1 is an illustration of a wavelength equalizer, also often referred to as a wavelength blocker.

FIG. 2 is an illustration of a wavelength equalizing array containing six wavelength equalizers.

FIG. 3 is an illustration of three wavelength equalizing arrays; one containing ten wavelength equalizers, one containing twelve wavelength equalizers, and one containing u wavelength equalizers.

FIG. 4 is an illustration of a first embodiment of a wavelength equalizing array containing six wavelength equalizers that can be configured to be any combination of 1 by 1 wavelength selective switches or 2 by 1 wavelength selective switches.

FIG. 5 is an illustration of a second embodiment of a wavelength equalizing array containing six wavelength equalizers that can be configured to be any combination of 1 by 1 wavelength selective switches or 2 by 1 wavelength selective switches.

FIG. 6 is an illustration of a wavelength equalizing array containing ten wavelength equalizers that can be configured to be any combination of 1 by 1 wavelength selective switches or 2 by 1 wavelength selective switches.

FIG. 7 is an illustration of a wavelength equalizing array containing six wavelength equalizers that can be configured to be any combination of 1 by 1 wavelength selective switches, 2 by 1 wavelength selective switches, or 3 by 1 wavelength selective switches.

FIG. 8 is an illustration of a wavelength equalizing array containing twelve wavelength equalizers that can be configured to be any combination of 1 by 1 wavelength selective switches, 2 by 1 wavelength selective switches, or 3 by 1 wavelength selective switches.

FIG. 9 is an illustration of an optical node comprising of a two degree ROADM on a circuit pack with an external multiplexer/de-multiplexer circuit pack.

FIG. 10 is an illustration of an optical node comprising of a two degree ROADM on a circuit pack utilizing a wavelength equalizing array containing six wavelength equalizers, with an external multiplexer/de-multiplexer circuit pack.

FIG. 11 is an illustration of an alternative embodiment optical node comprising of a two degree ROADM on a circuit pack utilizing a wavelength equalizing array containing six wavelength equalizers, with an external multiplexer/de-multiplexer circuit pack.

FIG. 12 is an illustration of an optical node comprising of a three degree ROADM on a circuit pack with an external multiplexer/de-multiplexer circuit pack.

FIG. 13 is an illustration of an optical node comprising of a three degree ROADM on a circuit pack utilizing a wavelength equalizing array containing twelve wavelength equalizers, with an external multiplexer/de-multiplexer circuit pack.

FIG. 14 is an illustration of an alternative embodiment of an optical node comprising of a three degree ROADM on a circuit pack utilizing a wavelength equalizing array containing twelve wavelength equalizers, with an external multiplexer/de-multiplexer circuit pack.

FIG. 15 is an illustration of a two degree optical node comprising of a two degree ROADM on a circuit pack that can be expanded to a four degree optical node.

FIG. 16A is an illustration of a 4-degree optical node comprising of two 2-degree ROADMs, with a single external multiplexer/de-multiplexer circuit pack.

FIG. 16B is an illustration of a 4-degree optical node comprising of two 2-degree ROADMs, with two external multiplexer/de-multiplexer circuit packs.

FIG. 17 is an illustration of a two-degree optical node utilizing a wavelength equalizing array comprising of a two degree ROADM on a circuit pack that can be expanded to a four degree optical node, with an external multiplexer/de-multiplexer circuit pack.

FIG. 18 is an illustration of an alternative embodiment of an optical node comprising of a two degree ROADM on a circuit pack that can be expanded to a four degree optical node, with an external multiplexer/de-multiplexer circuit pack.

FIG. 19 is an illustration of an optical node comprising of a 2-degree ROADM on a circuit pack that contains two optical channel monitors utilizing photo diodes.

FIG. 20 is an illustration of an optical node comprising of a two degree ROADM on a circuit pack with internal transponders, and an external multiplexer/de-multiplexer circuit pack.

FIG. 21 is an illustration of an optical node comprising of a three degree ROADM on a circuit pack with internal transponders, and an external multiplexer/de-multiplexer circuit pack.

FIG. 22 is an illustration of a first embodiment of an optical node comprising of an expandable two degree ROADM on a circuit pack with internal transponders, and an external multiplexer/de-multiplexer circuit pack.

FIG. 23 is an illustration of a second embodiment of an optical node comprising of an expandable two degree ROADM on a circuit pack with internal transponders, and an external multiplexer/de-multiplexer circuit pack.

FIG. 24 is an illustration of a third embodiment of an optical node comprising of an expandable two degree ROADM on a circuit pack, and an external multiplexer/de-multiplexer circuit pack with internal transponders.

FIG. 25 is an illustration of a ROADM circuit pack comprising of a wavelength equalizing array and front panel pluggable amplifiers.

FIG. 26 is an alternative illustration of a ROADM circuit pack comprising of a wavelength equalizing array and front panel pluggable amplifiers.

FIG. 27 is a flow diagram corresponding to a method of constructing a multi-degree optical node utilizing a wavelength equalizing array.

FIG. 28 is an illustration of an optical node comprising of a two degree ROADM on a circuit pack with embedded individual add/drop ports, and an external multiplexer/de-multiplexer circuit pack, and external transponders.

FIG. 29 is an illustration of an optical node comprising of a two degree ROADM on a circuit pack with embedded individual add/drop ports and an internal wavelength generator/receiver, and an external multiplexer/de-multiplexer circuit pack, and external transponders.

FIG. 30 is an illustration of an optical node comprising of a two degree ROADM on a circuit pack with an embedded individual add/drop port and an internal wavelength generator/receiver, and an external multiplexer/de-multiplexer circuit pack, and an external transponder.

FIG. 31 is an illustration of a two-degree optical node comprised of two ROADMs with embedded individual directionless add/drop ports.

FIG. 32 is an illustration of a two-degree optical node comprised of two ROADM circuit packs with embedded individual directionless add/drop ports, each ROADM circuit pack constructed using a wavelength equalizing array.

FIG. 33A is an illustration of a wavelength equalizing array containing eight wavelength equalizers that can be configured to be any combination of 1 by 1 wavelength selective switches or 2 by 1 wavelength selective switches or 1 by 2 wavelength selective switches.

FIG. 33B is a simplified schematic diagram of the wavelength equalizing array of FIG. 33A.

FIG. 33C is a simplified schematic diagram of a wavelength equalizing array like that of FIG. 33A, except it only contains six wavelength equalizers.

FIG. 34 is an illustration of a ROADM comprising of one optical degree, one degree express port, one add express port, and embedded add/drop ports.

FIG. 35 is the ROADM of FIG. 34 constructed using the wavelength equalizing array 3700 of FIG. 33A.

FIG. 36 is an illustration of a two-degree optical node comprised of two ROADMs with embedded individual directionless add/drop ports.

FIG. 37 is an illustration of a two-degree optical node comprised of two ROADMs with embedded individual add/drop ports.

FIG. 38A is an illustration of a ROADM with two operating modes constructed using the wavelength equalizing array 3700 of FIG. 33A.

FIG. 38B is the ROADM of FIG. 38A configured to mimic the ROADM of FIG. 36.

FIG. 38C is the ROADM of FIG. 38A configured to mimic the ROADM of FIG. 37.

FIG. 38D is a more detailed diagram of the 1 by 6 wavelength selective switch function of the ROADM of FIG. 38C.

FIG. 39A is an illustration of a wavelength switch containing two wavelength equalizers that can be configured to be two 1 by 1 wavelength selective switches or one 1 by 2 wavelength selective switch or one 2 by 1 wavelength selective switch.

FIG. 39B is an illustration of the wavelength switch of 39A configured as two 1 by 1 wavelength selective switches.

FIG. 39C is an illustration of the wavelength switch of 39A configured as one 1 by 2 wavelength selective switch.

FIG. 39D is an illustration of the wavelength switch of 39A configured as one 2 by 1 wavelength selective switch.

FIG. 40A is a wavelength switch containing four of the wavelength switches of FIG. 39A.

FIG. 40B is a simplified schematic diagram of the wavelength switch of FIG. 40A.

FIG. 41 is a two-degree node that uses two instances of the ROADM (4200) of FIG. 38A configured to mimic the optical node (4000) of FIG. 36.

FIG. 42 is a two-degree node that uses two instances of the ROADM (4200) of FIG. 38A configured to mimic the optical node (4100) of FIG. 37.

FIG. 43 is a two-degree node that uses two instances of the ROADM 4550 configured to mimic the optical node (4000) of FIG. 36.

FIG. 44 is a two-degree node that uses two instances of the ROADM 4550 configured to mimic the optical node (4100) of FIG. 37.

FIG. 45 is a software programmable single-degree ROADM.

FIG. 46A is the single-degree ROADM (5000) of FIG. 45 configured as a single-degree ROADM with one express port.

FIG. 46B is a simplified version of the ROADM of FIG. 46A.

FIG. 47A is the single-degree ROADM (5000) of FIG. 45 configured as a single-degree ROADM with two express ports.

FIG. 47B is a simplified version of the ROADM of FIG. 47A.

FIG. 48A is the single-degree ROADM (5000) of FIG. 45 configured as a single-degree ROADM with three express ports.

FIG. 48B is a simplified version of the ROADM of FIG. 48A.

FIG. 49A is the single-degree ROADM (5000) of FIG. 45 configured as a single-degree ROADM with four express ports.

FIG. 49B is a simplified version of the ROADM of FIG. 49A.

DETAILED DESCRIPTION

A description of example embodiments of the invention follows.

FIG. 1 is an illustration of a wavelength equalizer 100 comprising of; a wavelength de-multiplexer (DMUX) 101 that is used to separate a composite Wavelength Division Multiplexed (WDM) signal arriving at input 104 into r number of individual wavelengths, a plurality of Electrical Variable Optical Attenuators (EVOAs) 103 used to partially or fully attenuate the individual wavelengths, and a wavelength multiplexer (MUX) 102 that is used to combine r number of individual wavelengths into a composite Wavelength Division Multiplexed (WDM) signal for transmission at output 105. In addition to its optical elements (MUX, DMUX, and EVOAs), the wavelength equalizer 100 contains electronic circuitry (not shown) used to control the EVOAs, and a user interface (not shown) that is used to program the electronic circuitry of the EVOAs. The optical processing of each individual wavelength may be independently controlled. The optical power level of each individual wavelength may be attenuated by a programmable amount by sending a command through the user interface. The command is used by the electronic circuitry to set the attenuation value of the appropriate EVOA. Additionally, each individual EVOA can be program to substantially block the light associated with an incoming optical wavelength. Controlled attenuation ranges for typical EVOAs are 0 to 15 dB, or 0 to 25 dB. Blocking attenuation is typically 35 dB or 40 dB.

The device 100 is referred to as a wavelength equalizer because the EVOAs 103 can be used to equalize the power levels of all the wavelengths inputted into the device. Therefore, if wavelengths with unequal power levels are applied to input 104, the EVOAs can be configured so that the wavelengths exiting at 105 have substantially the same optical power level with respect to one another. The device 100 is also often referred to as a wavelength blocker, or as a one-by-one wavelength selective switch.

FIG. 2 is an illustration of a wavelength equalizing array 200 contained within a single device. The wavelength equalizing array 200 contains six wavelength equalizers 201 a-f that may be of the type 100 illustrated in FIG. 1. The wavelength equalizing array 200 contains six optical inputs (IN1-IN6) 202 a-f that are attached to the inputs of the wavelength equalizers, and six optical outputs (OUT1-OUT6) 203 a-f that are attached to the outputs of the wavelength equalizers. The electronic circuitry (not shown) used to control the EVOAs 204 may reside within the wavelength equalizing array device, or may reside external to the wavelength equalizing array device.

FIG. 3 (300) is an illustration of three different wavelength equalizing arrays 310 350, and 380. Each array may be contained within a single device. Wavelength equalizing array 310 contains ten wavelength equalizers that may be of the type 100 illustrated in FIG. 1. Wavelength equalizing array 350 contains twelve wavelength equalizers that may be of the type 100 illustrated in FIG. 1. Wavelength equalizing array 380 contains u wavelength equalizers that may be of the type 100 illustrated in FIG. 1 (wherein u can be any integer value). Although wavelength equalizing arrays 200, 310, 350 and 380 illustrate arrays with six, ten, twelve and u wavelength equalizers respectively, in general there is no limit to the number of wavelength equalizers that can be placed within a single device. Therefore, arrays with sixteen, twenty-four, or thirty-two wavelength equalizers may be possible.

Multiple different technologies may be used to implement the wavelength equalizing arrays 200, 310, 350 and 380, including Planer Lightwave Circuit (PLC) technology and various free-space optical technologies such as Liquid Crystal on Silicon (LCoS). A single Liquid Crystal on Silicon substrate may be used to implement a wavelength equalizing array containing any number of wavelength equalizers. The Wavelength Processing Array (WPA-12) from Santec Corporation is an example of a commercially available wavelength equalizing array containing twelve wavelength equalizers. The wavelength equalizing arrays 200, 310, 350 and 380 may be implemented by placing PLC based EVOAs and multiplexers (Arrayed Waveguide Gratings (AWG)) on a single substrate.

PLC based technologies and free-space optical technologies also provide the means to augment the wavelength equalizing arrays with additional components in order to realize additional functionality. An example of this is illustrated in FIG. 4. FIG. 4 illustrates a wavelength equalizing array 400 that contains six wavelength equalizers 100 a-f augmented with some additional optical components comprising of 1×2 optical switches, 2×1 optical switches, and variable optical couplers. The additional components provide the ability for two wavelength equalizers to perform either a 2 by 1 or 1 by 2 wavelength selective switch (WSS) function. A 1 by p wavelength selective switch is defined to be an optical device—with one WDM input port and p WDM output ports—that can be configured to direct individual wavelengths arriving on its input port to any of its p output ports. Similarly, a p by 1 wavelength selective switch is defined to be an optical device—with one WDM output port and p WDM input ports—that can be configured to direct individual wavelengths arriving on any of its input ports to its single output port.

In FIG. 4 three 2 by 1 WSS functions are implemented 401 a-c. For 2 by 1 WSS 401 a, the variable coupler 404 a is used to combine the wavelengths from wavelength equalizers 100 a and 100 b. For this case, 1 by 2 optical switches 402 a and 403 a are both configured to forward their incoming wavelengths to variable coupler 404 a, and variable coupler 404 a is configured as a 50/50 optical coupler (i.e., a coupler that forwards an equal amount of light from each of its two inputs). If wavelength number 1 (with frequency 1) is routed from IN1 406 a to OUT1 407 a, then wavelength number 1 (with frequency 1) arriving at IN2 406 b must be blocked by wavelength equalizer 100 b so as not to cause contention with the wavelength number 1 exiting wavelength equalizer 100 a. By appropriately blocking and passing wavelengths through 100 a and 100 b, up to r number of wavelengths may exit through port OUT1 407 a.

The variable coupler 404 a provides the ability to forward unequal amounts of light from wavelength equalizers 100 a and 100 b to output port OUT1. This may be a useful feature when, for example, the wavelengths arriving at input port IN1 406 a all have substantially lower optical power levels than the wavelengths arriving at input port IN2 406 b. For this case, variable attenuator 404 a may be programmed to allow more light from 100 a and less light from 100 b. Alternatively, the variable coupler 404 a may be replaced with a fixed coupler that forwards an equal amount of light from each of its two inputs.

In FIG. 4, optical switches 402 a, 403 a, and 405 a, provide the ability for the two wavelength equalizers 100 a and 100 b to be configured as either individual 1 by 1 WSS functions or a single 2 by 1 WSS function. When switches 402 a and 403 a are configured to switch their input light to coupler 404 a, then the two wavelength equalizers 100 a and 100 b are configured as a single 2 by 1 WSS. When switches 402 a and 403 a are configured to switch their input light away from coupler 404 a, then the two wavelength equalizers 100 a and 100 b are configured as individual 1 by 1 WSS functions. Switch 405 a is used to switch the output port OUT1 407 a between the two functionalities (i.e., either a single 2 by 1 WSS or a single 1 by 1 WSS function).

The optical circuitry within the optical block 401 a is used to direct optical wavelengths from the inputs 406 a-b of the optical block to the outputs 407 a-b of the optical block. Therefore, the optical circuitry within the optical block 401 a can be referred to as a wavelength directing function, or simply a wavelength director. The first optical input 406 a is used to provide a first source of wavelengths to the wavelength directing function within 401 a, and the second optical input 406 b is used to provide a second source of wavelengths to the wavelength directing function within 401 a. The first optical output 407 a is used to output a first set of wavelengths from the wavelength directing function within 401 a, and the second optical output 407 b is used to output a second set of wavelengths from the wavelength directing function within 401 a.

It may also be stated that the wavelength directing function 401 a is operable to implement a first mode and a second mode. The wavelength directing function is placed in the first mode by configuring optical switch 402 a to direct its input signal to optical switch 405 a (and not to coupler 404 a), and by configuring optical switch 405 a to direct its input signal from switch 402 a to the first optical output 407 a, and by configuring optical switch 403 a to direct its input signal to the second optical output 407 b (and not to the coupler 404 a). In this first mode of operation, the wavelength directing function operates as two independent 1 by 1 WSS functions. The first 1 by 1 WSS function comprises: wavelength equalizer 100 a, optical input 406 a, and optical output 407 a. The first optical input 406 a is used to provide a source of wavelengths to the wavelength equalizer 100 a. The wavelength equalizer 100 a is operable to pass and block individual wavelengths from the input 406 a to the output 407 a. A given wavelength at input 406 a is blocked from appearing at output 407 a by programming the EVOA associated with the given wavelength such that the EVOA substantially blocks the light associated with given wavelength. A given wavelength at input 406 a is passed to output 407 a by programming the EVOA associated with the given wavelength to not attenuate the given wavelength, or by programming the EVOA associated with the given wavelength to only partially attenuate the give wavelength. The second 1 by 1 WSS function comprises: wavelength equalizer 100 b optical input 406 b, and optical output 407 b. The second optical input 406 b is used to provide a source of wavelengths to the wavelength equalizer 100 b. The wavelength equalizer 100 b is operable to pass and block individual wavelengths from the input 406 b to the output 407 b. A given wavelength at input 406 b is blocked from appearing at output 407 b by programming the EVOA associated with the given wavelength such that the EVOA substantially blocks the light associated with the given wavelength. A given wavelength at input 406 b is passed to output 407 b by programming the EVOA associated with the given wavelength to not attenuate the given wavelength, or by programming the EVOA associated with the given wavelength to only partially attenuate the give wavelength. Each individual wavelength present at input 406 a may be individually and independently programmed to be either passed to the output 407 a or blocked from appearing at the output 407 a, as each of the r number of EVOAs (one for each of the r possible number of wavelengths present at input 406 a) is able to be independently programmed with no regard to how any of the other EVOAs within 100 a are programmed. Similarly, each individual wavelength present at input 406 b may be individually and independently programmed to be either passed to the output 407 b or blocked from appearing at the output 407 b.

When in the first mode, the wavelength directing function is not operable to pass and block individual wavelengths from the first optical input 406 a to the second optical output 407 b. This is because there no optical path exists between input 406 a and 407 b within 401 a. When in the first mode, the wavelength directing function is not operable to pass and block individual wavelengths from the second optical input 406 b to the first optical output 407 a. This is because optical switch 403 a is set to direct all wavelengths exiting wavelength equalizer 100 b to optical output 407 b.

The wavelength directing function of 401 a is placed in the second mode by configuring optical switch 402 a to direct its input signal to coupler 404 a (and not to optical switch 405 a), and by configuring optical switch 405 a to direct its input signal from coupler 404 a to the first optical output 407 a, and by configuring optical switch 403 a to direct its input signal to the coupler 404 a (and not to the second optical output 407 b). In this second mode of operation, the wavelength directing function operates as a 2 by 1 WSS function. The 2 by 1 WSS function comprises: wavelength equalizer 100 a, wavelength equalizer 100 b, optical coupler 404 a, optical input 406 a, optical input 406 b, and optical output 407 a. The first optical input 406 a is used to provide a first source of wavelengths to the 2 by 1 WSS function, and the second optical input is used to provide a second source of wavelengths to the 2 by 1 WSS function. The coupler 404 a is used to combine the wavelengths programmed to pass through wavelength equalizer 100 a with wavelengths programmed to pass through wavelength equalizer 100 b. Therefore, it can be stated that the wavelength equalizer 100 a is operable to pass and block individual wavelengths from the input 406 a to the output 407 a, and wavelength equalizer 100 b is operable to pass and block individual wavelengths from the input 406 b to the output 407 a, or more generally, when in the second mode, the wavelength directing function within 401 a is operable to pass and block wavelengths from the first optical input 406 a to the first optical output 407 a, and the wavelength directing function within 401 a is operable to pass and block wavelengths from the second optical input 406 b to the first optical output 407 a. Since there is no optical path from the first optical input 406 a to the second optical output 407 b, when in the second mode, the wavelength directing function is not operable to pass and block individual wavelengths from the first optical input 406 a to the second optical output 407 b. Also, since when in the second mode optical switch 403 a directs all wavelengths exiting wavelength equalizer 100 b to the optical coupler 404 a (and not to the output 407 b), when in the second mode, the wavelength directing function within 401 a is not operable to pass and block individual wavelengths from the second optical input 406 b to the second optical output 407 b.

The operation of optical switches 402 a, 403 a, and 405 a may be controlled using electrical signals. In one embodiment, a first electrical signal controls the state of optical switch 402 a. When the first electrical signal is set to a first state, the optical switch 402 a directs its input signal (including all wavelengths) to its output signal connected to optical switch 405 a. When the first electrical signal is set to a second state, the optical switch 402 a directs its input signal (including all wavelengths) to its output signal connected to optical coupler 404 a. In a similar manner, the state of optical switch 403 a may be controlled by a second electrical signal, and the state of optical switch 405 a may be controlled by a third electrical signal. The second electrical signal will have a first state (that connects the output of wavelength equalizer 100 b to the optical output 407 b), and a second state (that connects the output of wavelength equalizer 100 b to the coupler 404 a). Similarly, the third electrical signal will have a first state (that connects the output of optical switch 402 a to optical output 407 a) and a second state (that connects the output of optical coupler 404 a to the optical output 407 a). Since the first electrical signal, the second electrical signal, and the third electrical signal each have two states, the state of each of the three electrical signals may be controlled via a bit within a software register (one bit for each electrical signal, for a total of three bits). When software is used to program a given electrical signal to its first state, a logic zero may be written to the bit within the register associated with the given electrical signal. Similarly, when software is used to program a given electrical signal to its second state, a logic one may be written to the bit within the register associated with the given electrical signal. Therefore, in this manner the first mode and the second mode are software programmable. In order to program the wavelength directing function to the first mode, a logic zero is written to the three register bits associated with the first, second, and third electrical signals, and in order to program the wavelength directing function to the second mode, a logic one is written to the three register bits associated with the first, second, and third electrical signals. Since all three bits are always written with the same value (either three zeros or three ones), a single register bit may be used to control the mode of the wavelength directing function of 401 a. This is done by electrically connecting together the first electrical signal, the second electrical signal, and the third electrical signal, and then by driving this combination of signals using a signal register bit.

If coupler 404 a is a fixed coupler, no software control is required for it. If coupler 404 a is a variable optical coupler, then its coupling ratio may be controlled by an analog voltage signal that varies the coupling ratio based upon changing the amplitude of the analog voltage signal. A digital-to-analog converter may be used to control the analog voltage applied to the variable optical coupler. This would allow software to write a digital value to the digital-to-analog converter in order to set the coupling ratio of the variable optical coupler.

As illustrated in FIG. 4, wavelength equalizing array 400 comprises of three independently controlled wavelength directing functions 401 a-c. The second wavelength directing function within 401 b is operable to implement a third mode and a fourth mode (which are independent of the first and second mode of the first wavelength directing function of 401 a). A third optical input (IN3) to the wavelength equalizing array 400 is used to provide a first source of wavelengths to the second wavelength directing function 401 b, and a fourth optical input (IN4) to the wavelength equalizing array 400 is used to provide a second source of wavelengths to the second wavelength directing function 401 b. A third optical output from the wavelength equalizing array 400 (OUT3) is used to output a first set of wavelengths from the second wavelength directing function, and a fourth optical output from the wavelength equalizing array 400 (OUT4) is used to output a second set of wavelengths from the second wavelength directing function. The three optical switches within 401 b operate in an identical manner as the three switches within 401 a, and therefore may be used to place the second wavelength directing function in the third mode and the fourth mode. When programmed to be in the third mode, the second wavelength directing function operates as two independent 1 by 1 WSS functions, in a manner identical to the first mode of the first wavelength directing function 401 a. When programmed to be in the fourth mode, the second wavelength directing function operates as a 2 by 1 WSS function, in a manner identical to the second mode of the first wavelength directing function 401 a. Therefore, when in the third mode, the second wavelength directing function 401 b is operable to pass and block individual wavelengths from the third optical input (IN3) to the third optical output (OUT3) and from the fourth optical input (IN4) to the fourth optical output (OUT4), and the second wavelength directing function is not operable to pass and block individual wavelengths from the third optical input (IN3) to the fourth optical output (OUT4) and from the fourth optical input (IN4) to the third optical output (OUT4), and wherein when in the fourth mode, the second wavelength directing function 401 b is operable to pass and block individual wavelengths from the third optical input (IN3) to the third optical output (OUT3) and from the fourth optical input (IN4) to the third optical output (OUT3), and the second wavelength directing function 401 b is not operable to pass and block individual wavelengths from the third optical input (IN3) to the fourth optical output (OUT4). Additionally, when in the fourth mode, the second wavelength directing function 401 b is not operable to pass and block individual wavelengths from the fourth optical input (IN4) to the fourth optical output (OUT4).

If the electrical signal(s) that control the optical switches of the second wavelength directing function are separate and independent from the electrical signal(s) that control the optical switches of the first wavelength directing function, then the third mode and the fourth mode are independent of the first mode and the second mode, and the first mode and the second mode are independent of the third mode and the fourth mode.

The third wavelength directing function within 401 c is operable to implement a fifth mode and a sixth mode (which are independent of the first and second mode of the first wavelength directing function of 401 a, and also independent of the third and fourth mode of the second wavelength directing function of 401 b). A fifth optical input (IN5) to the wavelength equalizing array 400 is used to provide a first source of wavelengths to the third wavelength directing function 401 c, and a sixth optical input (IN6) to the wavelength equalizing array 400 is used to provide a second source of wavelengths to the third wavelength directing function 401 c. A fifth optical output from the wavelength equalizing array 400 (OUT5) is used to output a first set of wavelengths from the third wavelength directing function, and a sixth optical output from the wavelength equalizing array 400 (OUT6) is used to output a second set of wavelengths from the third wavelength directing function. The three optical switches within 401 c operate in an identical manner as the three switches within 401 a, and therefore may be used to place the second wavelength directing function in the fifth mode and the sixth mode. When programmed to be in the fifth mode, the third wavelength directing function operates as two independent 1 by 1 WSS functions, in a manner identical to the first mode of the first wavelength directing function 401 a. When programmed to be in the sixth mode, the third wavelength directing function operates as a 2 by 1 WSS function, in a manner identical to the second mode of the first wavelength directing function 401 a. Therefore, when in the fifth mode, the third wavelength directing function 401 c is operable to pass and block individual wavelengths from the fifth optical input (IN5) to the fifth optical output (OUT5) and from the sixth optical input (IN6) to the sixth optical output (OUT6), and the third wavelength directing function is not operable to pass and block individual wavelengths from the fifth optical input (IN5) to the sixth optical output (OUT6) and from the sixth optical input (IN6) to the fifth optical output (OUT5), and wherein when in the sixth mode, the third wavelength directing function 401 c is operable to pass and block individual wavelengths from the fifth optical input (IN5) to the fifth optical output (OUT5) and from the sixth optical input (IN6) to the fifth optical output (OUT5), and the third wavelength directing function 401 c is not operable to pass and block individual wavelengths from the fifth optical input (IN5) to the sixth optical output (OUT6). Additionally, when in the sixth mode, the third wavelength directing function 401 c is not operable to pass and block individual wavelengths from the sixth optical input (IN6) to the sixth optical output (OUT6).

If the electrical signal(s) that control the optical switches of the third wavelength directing function are separate and independent from the electrical signal(s) that control the optical switches of the first wavelength directing function and the second wavelength directing function, then the fifth mode and the sixth mode are independent of the first mode, the second mode, the third mode, and the fourth mode, and also, the first mode and the second mode and the third mode and the fourth mode are independent of the fifth mode and the sixth mode.

Additionally, the optical device 400 may be described without the concept of modes of operation by simply noting the possible paths between optical inputs and optical outputs within the device. From FIG. 4, it can be noted that there is an optical path between input 406 a and output 407 a, and there is an optical path between input 406 b and output 407 a, and there is an optical path between input 406 b and output 407 b, but there is no optical path that exists between input 406 a and output 407 b. Therefore optical device 400 comprises, a wavelength directing function 401 a, a first optical input 406 a used to provide a first source of wavelengths to the wavelength directing function 401 a, a second optical input 406 b used to provide a second source of wavelengths to the wavelength directing function 401 a, a first optical output 407 a used to output a first set of wavelengths from the wavelength directing function 401 a, and a second optical output 407 b used to output a second set of wavelengths from the wavelength directing function 401 a, wherein the wavelength directing function 401 a is operable to pass and block individual wavelengths from the first optical input 406 a to the first optical output 407 a and from the second optical input 406 b to the first optical output 407 a and from the second optical input 406 b to the second optical output 407 b, and wherein the wavelength directing function 401 a is not operable to pass and block individual wavelengths from the first optical input 406 a to the second optical output 407 b. The optical device 400 further comprises, a second wavelength directing function 401 b, a third optical input (IN3) used to provide a first source of wavelengths to the second wavelength directing function 401 b, a fourth optical input (IN4) used to provide a second source of wavelengths to the second wavelength directing function 401 b, a third optical output (OUT3) used to output a first set of wavelengths from the second wavelength directing function 401 b, and a fourth optical output (OUT4) used to output a second set of wavelengths from the second wavelength directing function 401 b, wherein the second wavelength directing function 401 b is operable to pass and block individual wavelengths from the third optical input (IN3) to the third optical output (OUT3) and from the fourth optical input (IN4) to the third optical output (OUT3) and from the fourth optical input (IN4) to the fourth optical output (OUT4), and wherein the second wavelength directing function 401 b is not operable to pass and block individual wavelengths from the third optical input (IN3) to the fourth optical output (OUT4). The optical device 400 further comprises, a third wavelength directing function 401 c, a fifth optical input (IN5) used to provide a first source of wavelengths to the third wavelength directing function 401 c, a sixth optical input (IN6) used to provide a second source of wavelengths to the third wavelength directing function 401 c, a fifth optical output (OUT5) used to output a first set of wavelengths from the third wavelength directing function 401 c, and a sixth optical output (OUT6) used to output a second set of wavelengths from the third wavelength directing function 401 c, wherein the third wavelength directing function 401 c is operable to pass and block individual wavelengths from the fifth optical input (IN5) to the fifth optical output (OUT5) and from the sixth optical input (IN6) to the fifth optical output (OUT5) and from the sixth optical input (IN6) to the sixth optical output (OUT6), and wherein the third wavelength directing function 401 c is not operable to pass and block individual wavelengths from the fifth optical input (IN5) to the sixth optical output (OUT6).

Note that it's possible to eliminate switches 402 a and 405 a when a variable coupler is used that can substantially direct to its output port all the light from one of its input ports. For this case, the output from 100 a is directly routed to the upper input of variable coupler 404 a, and the output of the optical coupler 404 a is connected directly to 407 a. Then when 401 a is programmed to be two individual 1 by 1 WSS functions, variable coupler 404 a is programmed to direct to its output all of the light from 100 a and none of the light from switch 403 a.

It can also be noted that each set of dual wavelength equalizers 401 a-c can be used as 1 by 2 WSS functions by inputting signals to port OUT1 407 a while outputting signals to ports IN1 406 a and IN2 406 b (i.e., operating the 2 by 1 WSS in the reverse direction).

It can also be noted that each set of dual wavelength equalizers 401 a-c can be independently programmed to be either a single 2 by 1 WSS function or two individual 1 by 1 WSS functions. As an example, 401 a may be programmed to be a 2 by 1 WSS function, while 401 b and 401 c may be programmed to be 1 by 1 WSS functions.

Although wavelength equalizing array 400 is shown as implemented with individual switches, multiplexers, and de-multiplexers, without departing from the spirit of the invention, the actual filtering and switching functions can be accomplished with other means, including using free-space optics wherein multiple switching and filtering functions are combined in order to accomplish the identical switching and filtering functionality.

FIG. 5 (500) illustrates an alternative method of implementing a six-input wavelength equalizing array 510 that can function as individual 1 by 1 WSS functions or 2 by 1 WSS functions or 1 by 2 WSS functions. The advantage of implementation 510 over implementation 400 is that the 2 by 1 WSS instances 511 a-c in 510 have lower insertion losses than the 2 by 1 WSS instances 401 a-c in 400. This is because implementation 510 eliminates the large insertion loss of the variable coupler 404 a. However, in order to eliminate the coupler, additional complexity is added in the form of 2r number of optical switch functions (1×2 and 2×1) 513, 514.

In the 510 implementation, individual 1 by 1 WSS functions are obtained by programming the optical switches 513 such that all wavelengths entering a given input INx are forwarded to the corresponding output OUTx. For instance, all the wavelengths entering input 515 a are forwarded to output 516 a, and not to output 516 b. When using dual wavelength equalizers to form a 2 by 1 WSS function (511 a, for example), the optical switches 513 are programmed such that all wavelengths entering IN1 515 a are forwarded to switches 514, and then switches 514 are used to route individual wavelengths to OUT2 516 b from either wavelengths entering on port IN1 515 a or port IN2 515 b.

An alternative structure for the dual wavelength equalizers is 511 d. In this structure r number of individual 1×2 switches are replaced with a single 1×2 broadband (waveguide) switch 520 at the expense of an extra DMUX.

The set of dual wavelength equalizers 511 a-c can operate as either 2 by 1 WSS functions or 1 by 2 WSS functions. For example, when operating instance 511 a as a 2 by 1 device, input ports IN1 515 a and IN2 515 b and output port OUT2 516 b are used. Alternatively, when operating instance 511 a as a 1 by 2 device, ports OUT1 516 a, OUT2 516 b and in IN1 515 a are used.

The dual wavelength equalizer 511 d can operate as a 1 by 2 WSS function by running the device backwards using OUT2 522 b as the input (not 522 a).

The optical circuitry within the optical block 511 a is used to direct optical wavelengths from the inputs 515 a-b of the optical block to the outputs 516 a-b of the optical block. Therefore, the optical circuitry within the optical block 511 a can be referred to as a wavelength directing function, or simply a wavelength director. The first optical input 515 a is used to provide a first source of wavelengths to the wavelength directing function within 511 a, and the second optical input 515 b is used to provide a second source of wavelengths to the wavelength directing function within 511 a. The first optical output 516 a is used to output a first set of wavelengths from the wavelength directing function within 511 a, and the second optical output 516 b is used to output a second set of wavelengths from the wavelength directing function within 511 a. In a first embodiment, each of the optical switches within the r number of optical switches of 513 may be programmed independent of one another. In second embodiment, each of the optical switches within the r number of optical switches of 513 may be programmed identically using a single control signal. Each of the optical switches within the r number of optical switches of 514 may be programmed independent of one another. In order to allow simultaneous selection of wavelengths from either IN1 or IN2 when operating 511 a as a 2 by 1 WSS function, each of the optical switches within the r number of optical switches of 514 must be able to be programmed independent of one another.

Like that of optical block 401 a, optical block 511 a is operable to implement a first mode and a second mode. The wavelength directing function 511 a is placed in the first mode by configuring all the optical switches of 513 to direct their input signals towards OUT1 (516 a), and by configuring all the optical switches of 514 to connect the input signals from IN2 (515 b) to output OUT2 (516 b). When the switches 513 and 514 are set in this manner, the wavelength directing function of 511 a operates as two independent 1 by 1 WSS functions, with the first 1 by 1 WSS function comprising IN1 (515 a) and OUT1 (516 a), and the second 1 by 1 WSS function comprising IN2 (515 b) and OUT2 (516 b). The wavelength directing function 511 a is placed in the second mode by configuring all the optical switches of 513 to direct their input signals towards OUT2 (516 b). When operating in the second mode, the wavelength directing function operates as a 2 by 1 WSS function, using inputs 515 a and 515 b and output 516 b. When operating in the second mode, optical switches 514 must be free to be programmed to select wavelengths from either IN1 (515 a) or IN2 (515 b), therefore, each of the r 2×1 switches of 514 must have an independent control signal (for a total of r independent control signals). When in the first mode, the wavelength directing function 511 a is operable to pass and block individual wavelengths from the first optical input 515 a to the first optical output 516 a and from the second optical input 515 b to the second optical output 516 b, and the wavelength directing function is not operable to pass and block individual wavelengths from the first optical input 515 a to the second optical output 516 b (due to the settings of switches 513 and 514) and from the second optical input 515 b to the first optical output 516 a (due to the settings of switches 513 and 514), and wherein when in the second mode, the wavelength directing function 511 a is operable to pass and block individual wavelengths from the first optical input 515 a to the second optical output 516 b and from the second optical input 515 b to the second optical output 516 b, and the wavelength directing function is not operable to pass and block individual wavelengths from the first optical input 515 a to the first optical output 516 a (due to the setting of switches 513). Also, when in the second mode, the wavelength directing function 511 a is not operable to direct wavelengths from the second optical input 515 b to the first optical output 516 a (since no path exists between optical input 515 b and optical output 516 a, regardless of optical switch settings).

In addition to operating in a first mode (two 1 by 1 WSS functions) and a second mode (one 2 by 1 WSS function), the wavelength directing function is operable to implement a third mode (one 1 by 2 WSS function). The wavelength directing function 511 a is placed in the third mode by configuring all the optical switches of 514 to direct input signals from IN1 (515 a) to OUT2 (516 b). When operating in the third mode, the wavelength directing function operates as a 2 by 1 WSS function, using input 515 a and outputs 516 a and 516 b. When operating in the third mode, optical switches 513 must be free to be programmed to direct wavelengths to either OUT1 (516 a) or OUT2 (516 b), therefore, each of the r 2×1 switches of 513 must have an independent control signal (for a total of r independent control signals). When in the third mode, the wavelength directing function 511 a is operable to pass and block individual wavelengths from the first optical input 515 a to the first optical output 516 a and from the first optical input 515 a to the second optical output 516 b, and the wavelength directing function is not operable to pass and block individual wavelengths from the second optical input 515 b to the second optical output 516 b (due to the setting of switches 514). Also, when in the third mode, the wavelength directing function 511 a is not operable to direct wavelengths from the second optical input 515 b to the first optical output 516 a (since no path exists between optical input 515 b and optical output 516 a, regardless of optical switch settings).

Additionally, the optical device 510 may be described without the concept of modes of operation by simply noting the possible paths between optical inputs and optical outputs within the device. From FIG. 5, it can be noted that there is an optical path between input 515 a and output 516 a, and there is an optical path between input 515 a and output 516 b, and there is an optical path between input 515 b and output 516 b, but there is no optical path that exists between input 515 b and output 516 a. Therefore optical device 510 comprises, a wavelength directing function 511 a, a first optical input 515 a used to provide a first source of wavelengths to the wavelength directing function 511 a, a second optical input 515 b used to provide a second source of wavelengths to the wavelength directing function 511 a, a first optical output 516 a used to output a first set of wavelengths from the wavelength directing function 511 a, and a second optical output 516 b used to output a second set of wavelengths from the wavelength directing function 511 a, wherein the wavelength directing function 511 a is operable to pass and block individual wavelengths from the first optical input 515 a to the first optical output 516 a and from the first optical input 515 a to the second optical output 516 b and from the second optical input 515 b to the second optical output 516 b, and wherein the wavelength directing function 511 a is not operable to pass and block individual wavelengths from the second optical input 515 b to the first optical output 516 a.

The optical device 510 further comprises, a second wavelength directing function 511 b, a third optical input (IN3) used to provide a first source of wavelengths to the second wavelength directing function 511 b, a fourth optical input (IN4) used to provide a second source of wavelengths to the second wavelength directing function 511 b, a third optical output (OUT3) used to output a first set of wavelengths from the second wavelength directing function 511 b, and a fourth optical output (OUT4) used to output a second set of wavelengths from the second wavelength directing function 511 b, wherein the second wavelength directing function 511 b is operable to pass and block individual wavelengths from the third optical input (IN3) to the third optical output (OUT3) and from the third optical input (IN3) to the fourth optical output (OUT4) and from the fourth optical input (IN4) to the fourth optical output (OUT4), and wherein the second wavelength directing function 511 b is not operable to pass and block individual wavelengths from the fourth optical input (IN4) to the third optical output (OUT3).

The optical device 510 further comprises, a third wavelength directing function 511 c, a fifth optical input (IN5) used to provide a first source of wavelengths to the third wavelength directing function 511 c, a sixth optical input (IN6) used to provide a second source of wavelengths to the third wavelength directing function 511 c, a fifth optical output (OUT5) used to output a first set of wavelengths from the third wavelength directing function 511 c, and a sixth optical output (OUT6) used to output a second set of wavelengths from the third wavelength directing function 511 c, wherein the third wavelength directing function 511 c is operable to pass and block individual wavelengths from the fifth optical input (IN5) to the fifth optical output (OUT5) and from the fifth optical input (IN5) to the sixth optical output (OUT6) and from the sixth optical input (IN6) to the sixth optical output (OUT6), and wherein the third wavelength directing function 511 c is not operable to pass and block individual wavelengths from the sixth optical input (IN6) to the fifth optical output (OUT5).

It should be noted that the wavelength directing function 511 a is operable to simultaneously pass and block individual wavelengths from the first optical input 515 a to the first optical output 516 a, and from the first optical input 515 a to the second optical output 516 b.

FIG. 6 shows a wavelength equalizing array 600 that is constructed identically to the wavelength equalizing array 510, except that array 600 contains ten wavelength equalizers instead of only six.

FIG. 7 shows a wavelength equalizing array 700 containing six wavelength equalizers 701 a-f that can be configured (by setting the 1×2, and 2×1 switches appropriately) as either 1 by 3 WSS functions, 1 by 2 WSS functions, 2 by 1 WSS functions, 3 by 1 WSS functions, or 1 by 1 WSS functions. A first 1 by 3 device is formed by the top three wavelength equalizers 701 a-c (using IN1 702 a, OUT1 703 a, OUT2 703 b, and OUT 3 703 c), while a second 1 by 3 device is formed by the bottom three wavelength equalizers 701 d-f (using IN4 702 d, OUT4 703 d, OUT5 703 e, and OUT 6 703 f). In order to use the wavelength equalizing array as 3 by 1 WSS functions, the wavelength equalizing array is used in the reverse direction, using all output ports as inputs, and using the IN1 port 702 a as the output port for the top 3 by 1, and using the IN4 port 702 d as the output port for the bottom 3 by 1. Alternatively, a first 3 by 1 WSS function is formed by the top three wavelength equalizers 701 a-c (using IN1 702 a, IN2 702 b, IN3 702 c, and OUT 3 703 c), while a second 3 by 1 WSS function is formed by the bottom three wavelength equalizers 701 d-f (using IN4 702 d, IN5 702 e, IN6 702 f, and OUT6 703 f).

The wavelength equalizing array 700 can alternatively be used to create three 1 by 2 WSS functions by using IN1 702 a, OUT1 703 a and OUT2 703 b as the first 1 by 2 WSS, using IN3 702 c, OUT3 703 c, and OUT4 703 d as the second 1 by 2 WSS, and using IN5 702 e, OUT5 703 e, and OUT6 703 f as the third 1 by 2 WSS. Similarly, the wavelength equalizing array 700 can be used to create three 2 by 1 WSS functions by using IN1 702 a, IN2 702 b, and OUT2 703 b as the first 2 by 1 WSS, using IN3 702 c, IN4 702 d, and OUT4 703 d as the second 2 by 1 WSS, and using IN5 702 e, IN6 702 f, and OUT6 703 f as the third 2 by 1 WSS.

Finally, the wavelength equalizing array 700 can be used to create six 1 by 1 WSS functions by programming all switches such that all input wavelengths arriving on a given port INx are forwarded to the corresponding output port OUTx.

It should also be noted that the structure of 700 provides the ability to form a 1 by 2 WSS function by using any two consecutive output ports on the structure of 700. For instance, a 1 by 2 WSS function can be formed using consecutive outputs OUT1 703 a and OUT2 703 b along with IN1 702 a, and a 1 by 2 WSS function can be formed using consecutive outputs OUT2 703 b and OUT3 703 c along with IN2 702 b, and a 1 by 2 WSS function can be formed using consecutive outputs OUT3 703 c and OUT4 703 d along with IN3 702 c, and a 1 by 2 WSS function can be formed using consecutive outputs OUT4 703 d and OUT5 703 e along with IN4 702 d, and a 1 by 2 WSS function can be formed using consecutive outputs OUT5 703 e and OUT6 703 f along with IN5 702 e.

It should also be noted that the structure of 700 provides the ability to form a 2 by 1 WSS function by using any two consecutive input ports on the structure of 700. For instance, a 2 by 1 WSS function can be formed using consecutive inputs IN1 702 a and IN2 702 b along with OUT2 703 b, and a 2 by 1 WSS function can be formed using consecutive inputs IN2 702 b and IN3 702 c along with OUT3 703 c, and a 2 by 1 WSS function can be formed using consecutive inputs IN3 702 c and IN4 702 d along with OUT4 703 d, and a 2 by 1 WSS function can be formed using consecutive inputs IN4 702 d and IN5 702 e along with OUT5 703 e, and a 2 by 1 WSS function can be formed using consecutive inputs IN5 702 e and IN6 702 f along with OUT6 703 f.

Any combination of 1 by 3 WSS functions, 1 by 2 WSS functions, 3 by 1 WSS functions, 2 by 1 WSS functions, and 1 by 1 WSS functions can be created using the wavelength equalizing array 700. For instance, wavelength equalizing array 700 can be used to implement a single 1 by 3 WSS function, a single 1 by 2 WSS function, and a single 1 by 1 WSS function. Alternatively, the wavelength equalizing array 700 can be used to implement two 1 by 2 WSS functions, and two 1 by 1 WSS functions. In this way, a single wavelength equalizing array device can be used in a product to create a product with multiple distinct capabilities, while not incurring the cost and complexity of creating a single 6 by 6 WSS function.

The optical device 700 may be described without the concept of modes of operation by simply noting the possible paths between optical inputs and optical outputs within the device. From FIG. 7, it can be noted that there is an optical path between input 702 a and output 703 a, and there is an optical path between input 702 a and output 703 b, and there is an optical path between input 702 b and output 703 b, but there is no optical path that exists between input 702 b and output 703 a. Therefore optical device 700 comprises, a wavelength directing function, a first optical input 702 a used to provide a first source of wavelengths to the wavelength directing function, a second optical input 702 b used to provide a second source of wavelengths to the wavelength directing function, a first optical output 703 a used to output a first set of wavelengths from the wavelength directing function, and a second optical output 703 b used to output a second set of wavelengths from the wavelength directing function, wherein the wavelength directing function a is operable to pass and block individual wavelengths from the first optical input 702 a to the first optical output 703 a and from the first optical input 702 a to the second optical output 703 b and from the second optical input 702 b to the second optical output 703 b, and wherein the wavelength directing function is not operable to pass and block individual wavelengths from the second optical input 702 b to the first optical output 703 a.

The optical device 700, further comprises, a third optical input 702 c used to provide a third source of wavelengths to the wavelength directing function, and a third optical output 703 c used to output a third set of wavelengths from the wavelength directing function, wherein the wavelength directing function is operable to pass and block individual wavelengths from the first optical input 702 a to the third optical output 703 c and from the second optical input 702 b to the third optical output 703 c and from the third optical input 702 c to the third optical output 703 c, and wherein the wavelength directing function is not operable to pass and block individual wavelengths from the third optical input 702 c to the first optical output 703 a and from the third optical input 702 c to the second optical output 703 b.

The optical device 700, further comprises, a fourth optical input 702 d used to provide a fourth source of wavelengths to the wavelength directing function, and a fourth optical output 703 d used to output a fourth set of wavelengths from the wavelength directing function, wherein the wavelength directing function is operable to pass and block individual wavelengths from the third optical input 702 c to the fourth optical output 703 d and from the fourth optical input 702 d to the fourth optical output 703 d, and wherein the wavelength directing function is not operable to pass and block individual wavelengths from the first optical input 702 a to the fourth optical output 703 d and from the second optical input 702 b to the fourth optical output 703 d and from the fourth optical input 702 d to the first optical output 703 a and from the fourth optical input 702 d to the second optical output 703 b and from the fourth optical input 702 d to the third optical output 703 c.

The optical device of 700, further comprises, a fifth optical input 702 e used to provide a fifth source of wavelengths to the wavelength directing function, and a fifth optical output 703 e used to output a fifth set of wavelengths from the wavelength directing function, wherein the wavelength directing function is operable to pass and block individual wavelengths from the fourth optical input 702 d to the fifth optical output 703 e and from the fifth optical input 702 e to the fifth optical output 703 e, and wherein the wavelength directing function is not operable to pass and block individual wavelengths from the first optical input 702 a to the fifth optical output 703 e and from the second optical input 702 b to the fifth optical output 703 e and from the third optical input 702 c to the fifth optical output 703 e and from the fifth optical input 702 e to the first optical output 703 a and from the fifth optical input 702 e to the second optical output 703 b and from the fifth optical input 702 e to the third optical output 703 c and from the fifth optical input 702 e to the fourth optical output 703 d.

The optical device of 700, further comprises, a sixth optical input 702 f used to provide a sixth source of wavelengths to the wavelength directing function, and a sixth optical output 703 f used to output a sixth set of wavelengths from the wavelength directing function, wherein the wavelength directing function is operable to pass and block individual wavelengths from the fourth optical input 702 d to the sixth optical output 703 f and from the fifth optical input 702 e to the sixth optical output 703 f and from the sixth optical input 702 f to the sixth optical output 703 f, and wherein the wavelength directing function is not operable to pass and block individual wavelengths from the first optical input 702 a to the sixth optical output 703 f and from the second optical input 702 b to the sixth optical output 703 f and from the third optical input 702 c to the sixth optical output 703 f and from the sixth optical input 702 f to the first optical output 703 a and from the sixth optical input 702 f to the second optical output 703 b and from the sixth optical input 702 f to the third optical output 703 c and from the sixth optical input 702 f to the fourth optical output 703 d and from the sixth optical input 702 f to the fifth optical output 703 e.

Although wavelength equalizing array 700 is shown as implemented with individual switches, multiplexers, and de-multiplexers, the actual switching functions can be accomplished with free-space optics wherein multiple switching and filtering functions are combined in order to accomplish identical switching and filtering functionality.

In general, for a wavelength equalizing array that can be configured as either 1 by 1 WSS functions or 2 by 1 WSS functions, if the device can be used to construct a maximum of n 1 by 1 WSS functions, then the maximum number of 2 by 1 WSS functions that the array can be used to create is n/2 devices, since each 2 by 1 device requires the resources associated with two 1 by 1 WSS functions.

For a wavelength equalizing array with a maximum of n number of 1 by 1 WSS functions that can be configured as either 1 by 1 WSS functions or 2 by 1 WSS functions, if the device is configured to have m number of 1 by 1 WSS functions, then the maximum number of 2 by 1 devices that can also be configured is equal to (n−m)/2.

For a wavelength equalizing array that can be configured as either 1 by 1 WSS functions or 3 by 1 WSS functions, if the device can be used to construct a maximum of n 1 by 1 WSS functions, then the maximum number of 3 by 1 WSS functions that the array can be used to create is n/3 devices, since each 3 by 1 device requires the resources associated with three 1 by 1 WSS functions.

For a wavelength equalizing array with a maximum of n number of 1 by 1 WSS functions that can be configured as either 1 by 1 WSS functions or 3 by 1 WSS functions, if the device is configured to have m number of 1 by 1 WSS functions, then the maximum number of 3 by 1 devices that can also be configured is equal to (n−m)/3.

In general, a wavelength equalizing array can be partitioned into an array of k₁ 1×1, k₂ 1×2, k₃ 1×3 . . . , k_(p) 1×p wavelength selective switches, where p is any integer number greater than 1, and k_(j) is any integer value greater than or equal to 0. For this case, if n is the maximum number of 1×1 wavelength selective switches in the at least one wavelength equalizing array, then Σ_(i=1) ^(p)i×k_(i)≤n.

FIG. 8 depicts a wavelength equalizing array 800 containing two instances (700 a, 700 b) of wavelength equalizing array 700. In FIG. 8, the wavelength equalizing array 800 can be partitioned into four 1 by 3 WSS functions 810 a-d.

FIG. 9 shows an optical node 900 comprising of a two-degree Reconfigurable Optical Add/Drop Multiplexer (ROADM) 910 on a circuit pack with an external multiplexer/de-multiplexer circuit pack 920. Each line interface on the ROADM (Line In/Out West 901 a-b, and Line In/OUT East 902 a-b) represents an optical degree. In addition, optical node 900 contains a port common to both optical degrees (common port 970 a-b) that is connectable to a plurality of directionless add/drop ports 961 and 960. Six wavelength equalizers 905 a-f are used in the design—three for each degree. Wavelength equalizer WE1 905 a is used to either pass or block wavelengths from the West Line interface 901 a to the multiplexer/de-multiplexer circuit pack 920 attached to the common port 970 a-b. Similarly, wavelength equalizer WE4 905 d is used to either pass or block wavelengths from the East Line interface 902 a to the multiplexer/de-multiplexer circuit pack 920 attached to the common port 970 a-b. The wavelengths from WE1 905 a and WE4 905 d are combined together using optical coupler 934, and then they are forwarded to the multiplexer/de-multiplexer circuit pack 920 via optional optical amplifier 942 through the common optical port 970 a.

Wavelength equalizer WE3 905 c is used to either pass or block wavelengths from the common port 970 b to the West Line interface 901 b. It is also used to equalize the power levels of the wavelengths exiting out the West Line interface 901 b from the multiplexer/de-multiplexer circuit pack 920. Similarly, wavelength equalizer WE6 905 f is used to either pass or block wavelengths from the common port 970 b to the East Line interface 902 b. It is also used to equalize the power levels of the wavelengths exiting out the East Line interface 902 b from the multiplexer/de-multiplexer circuit pack 920.

Wavelength equalizer WE2 905 b is used to either pass or block wavelengths from the East Line interface 902 a to the West Line interface 901 b. It is also used to equalize the power levels of the wavelengths exiting out the West Line interface 901 b from the East Line interface 902 a. Similarly, wavelength equalizer WE5 905 e is used to either pass or block wavelengths from the West Line interface 901 a to the East Line interface 902 b. It is also used to equalize the power levels of the wavelengths exiting out the East Line interface 902 b from the West Line interface 901 a.

Optional input optical amplifiers 940 a-b are used to optically amplify wavelengths arriving from the West 901 a and East 902 a Line interfaces. These amplifiers can be constructed using Erbium Doped Fiber Amplifier (EDFA) technology or some other suitable technology.

Optical coupler 930 is used to broadcast all the wavelengths from the West Line interface 901 a to both wavelength equalizer WE1 905 a and WE5 905 e. Similarly, optical coupler 932 is used to broadcast all the wavelengths from the East Line interface 902 a to both wavelength equalizer WE2 905 b and WE4 905 d.

Optical coupler 931 is used to combine the wavelengths from wavelength equalizers WE2 905 b and WE3 905 c into one composite WDM signal that is optically amplified with output optical amplifier 941 a. Similarly, optical coupler 933 is used to combine the wavelengths from wavelength equalizers WE5 905 e and WE6 905 f into one composite WDM signal that is optically amplified with output optical amplifier 941 b.

Optional optical amplifier 943 receives added wavelengths from the multiplexer/de-multiplexer circuit pack 920 via port 970 b, and optically amplifies the wavelengths before forwarding the amplified wavelengths to optical coupler 935. Optical coupler 935 is used to broadcast the added wavelengths to both the West Line interface 901 b and East Line interface 902 b via WE3 905 c and WE6 905 f respectively.

Located on the multiplexer/de-multiplexer circuit pack 920 is a plurality (r) of add/drop ports 961, 960. Individual wavelengths are added to the multiplexer/de-multiplexer circuit pack and then multiplexed via multiplexer 951 into a composite WDM signal that is then forwarded to the ROADM circuit pack 910. In the drop direction on 920, a composite WDM signal is received from the common port 970 a of the ROADM circuit pack 910 and then it is de-multiplexed into individual wavelengths using de-multiplexer 950. Each de-multiplexed wavelength is then forwarded to a specific drop port 960 of the de-multiplexer. The multiplexer and de-multiplexer may be implemented using Arrayed Waveguide Grating (AWG) technology, or some other suitable technology. Devices that process individual wavelengths for transmission—such as optical transponders—can be used to supply and receive wavelengths to and from the add/drop ports. The common port 970 a-b of the ROADM circuit pack 910 is connected to the multiplexer/de-multiplexer circuit pack 920 using two optical jumper interconnections 972 a-b.

As can be seen in 900, a single multiplexer/de-multiplexer circuit pack is used to add and drop wavelengths to/from both the East and West Line interfaces. Therefore, a transponder that is attached to an add/drop port of the multiplexer/de-multiplexer circuit pack 920, can forward and receive wavelengths to and from any of the two degrees of the ROADM circuit pack. Because of this, the add/drop ports are referred to as directionless add/drop ports—meaning the add drop ports are not dedicated to a particular direction of the optical node. The wavelength equalizers on the ROADM circuit pack are used to steer the added and dropped wavelengths to and from each degree by appropriately blocking or passing wavelengths. Therefore, the wavelength equalizers WE1 905 a, WE3 905 c, WE4 905 d, and WE6 905 f are said to perform directionless steering for the add/drop ports for each degree.

Additionally, the wavelength equalizers on the ROADM circuit pack are used to select which wavelengths from the Line input interfaces are allowed to exit a given output interface (degree), by appropriately blocking or passing wavelengths.

Both the ROADM circuit pack 910 and the multiplexer/de-multiplexer circuit pack 920 may contain electrical connectors that allow the two circuit packs to be plugged into an electrical back plane of an electrical shelf (not shown). The multiplexer/de-multiplexer circuit 920 pack may contain active components (i.e., components requiring electrical power in order to operate), or it may contain only passive components (athermal AWGs, for example). If the multiplexer/de-multiplexer circuit pack 920 contains only passive components, then the multiplexer/de-multiplexer circuit pack could optionally be placed outside of the electrical shelf.

FIG. 10 shows a two-degree optical node 1000 that is identical to the optical node 900, except that a single wavelength equalizing array 200 is used to supply all the required wavelength equalizers needed to construct the optical node. (Alternatively, multiple smaller wavelength equalizing arrays could be utilized.) The wavelength equalizers WE1-WE6 in 1000 correspond to the wavelength equalizers WE1-WE6 in 900. More specifically WE1 1005 a in ROADM circuit pack 1010 corresponds WE1 905 a in ROADM circuit pack 910, WE2 1005 b in 1010 corresponds WE2 905 b in 910, WE3 1005 c in 1010 corresponds WE3 905 c in 910, WE4 1005 d in 1010 corresponds WE4 905 d in 910, WE5 1005 e in 1010 corresponds WE5 905 e in 910, and WE6 1005 f in 1010 corresponds WE6 905 f in 910. Likewise, the optical couplers 1030, 1031, 1032, 1033, 1034, and 1035 perform the same functions as their respective counterparts 930, 931, 932, 933, 934, and 935 within ROADM circuit pack 1010. The single wavelength equalizing array 200 may be identical to the wavelength equalizing array 200 discussed in reference to FIG. 2.

A single ROADM circuit pack 1010 supplies all the required optical circuitry to construct an optical node with two optical degrees, including input and output amplifiers for each degree, a common port 1070 a-b connectable to a plurality of directionless add/drop ports, optical supervisory channel circuitry (not shown), optical channel monitoring (not shown), and a single wavelength equalizing array 200 that is used to both select wavelengths for each optical degree (using WE2 1005 b and WE3 1005 c for the West degree 1001 b, and using WE5 1005 e and WE6 1005 f for the East degree 1002 b) and to perform directionless steering for the plurality of directionless add/drop ports (using WE1 1005 a and WE4 1005 d in the drop direction, and using WE3 1005 c and WE6 1005 f in the add direction).

As can be seen in 1000, a single multiplexer/de-multiplexer circuit pack 1020 is used to add and drop wavelengths to/from both the East 1002 a-b and West 1001 a-b Line interfaces. Therefore, a transponder (not shown) that is attached to an add/drop port of the multiplexer/de-multiplexer circuit pack 1020, can forward and receive wavelengths to/from any of the two degrees of the ROADM circuit pack. Because of this, the add/drop ports are referred to as directionless add/drop ports—meaning the add drop ports are not dedicated to a particular direction of the optical node. The wavelength equalizers on the ROADM circuit pack are used to steer the added and dropped wavelengths to and from each degree by appropriately blocking or passing wavelengths. Therefore, the wavelength equalizers are said to perform directionless steering for the add/drop ports.

Additionally, the wavelength equalizers on the ROADM circuit pack 1010 are used to select which wavelengths from the Line input interfaces are allowed to exit a given output interface (degree), by appropriately blocking or passing wavelengths.

The wavelength equalizing array saves physical space and electrical power by utilizing common optics and electronics for all the wavelength equalizers in the array, thus making it more suitable for low-cost compact edge-of-network applications. The single wavelength equalizing array also provides a means to simplify the construction of the ROADM circuit pack that it is placed upon.

A preferred embodiment utilizes a “single” wavelength equalizing array to construct an optical node. Other embodiments may include using more than one wavelength equalizing array.

A preferred embodiment is to construct an optical node of at least two optical degrees using both a first circuit pack and a second circuit pack, wherein the optical node contains at least one wavelength equalizing array and a plurality of directionless add/drop ports, and wherein the at least one wavelength equalizing array is contained on the first circuit pack, and wherein the plurality of direction less add/drop ports are contained on the second circuit pack.

Another embodiment comprises of an optical node of at least two optical degrees, implemented using a single circuit pack, wherein the optical node contains at least one wavelength equalizing array and a plurality of directionless add/drop ports, and wherein the at least one wavelength equalizing array and the plurality of directionless add/drop ports are contained on the single circuit pack.

Another preferred embodiment includes a ROADM circuit pack, comprising of at least two optical degrees, and a common port connectable to a plurality of directionless add/drop ports, wherein wavelengths from the common port may be directed to any of the at least two optical degrees. Additionally, wavelengths from the at least two optical degrees may be directed to the common port of the ROADM circuit pack. The embodiment may further include input optical amplification and output optical amplification for each optical degree. The ROADM circuit pack may further comprise of at least one wavelength equalizing array, wherein the at least one wavelength equalizing array provides a means to both select wavelengths for each degree, and to perform directionless steering of wavelengths to and from the plurality of directionless add/drop ports, as illustrated in reference to the ROADM shown in FIG. 10. In a preferred embodiment, a single wavelength equalizing array is used to construct the ROADM circuit pack. The at least one wavelength equalizing array may be constructed using a single Liquid Crystal on Silicon substrate, or it may be constructed using planar lightwave circuitry.

FIG. 11 shows a two-degree optical node 1100 that is identical to the optical node 900, except that a single wavelength equalizing array 510 is used to supply all the required wavelength equalizers needed to construct the optical node. The wavelength equalizing array 510 may be identical to the wavelength equalizing array that was described in reference to FIG. 5.

This wavelength equalizing array 510 can be configured to perform the function of multiple 2 by 1 WSS functions. Therefore, the function of the optical couplers 931, 933, and 934 of optical node 900 are additionally absorbed within the wavelength equalizing array 510. The 2 by 1 WSS function 511 aa performs the function of WE1 905 a, WE4 905 d, and optical coupler 934 within optical node 900, while the 2 by 1 WSS function 511 bb performs the function of WE2 905 b, WE3 905 c, and optical coupler 931 within optical node 900, and the 2 by 1 WSS function 511 cc performs the function of WE5 905 e, WE6 905 f, and optical coupler 933 within optical node 900. Optical couplers 1130, 1132, and 1135 perform the same functions as their respective counterparts 930, 932, and 935 within ROADM circuit pack 910. As can be seen from FIG. 11, using the wavelength equalizing array 510 in place of wavelength equalizing array 200 further simplifies the ROADM circuit pack due to the additional level of integration.

FIG. 12 shows an optical node 1200 comprising of a three-degree Reconfigurable Optical Add/Drop Multiplexer (ROADM) 1210 on a circuit pack with an external multiplexer/de-multiplexer circuit pack 1220. Each line interface on the ROADM (Line In/Out West 1201 a-b, Line In/OUT East 1202 a-b, and Line In/OUT South 1203 a-b) represents an optical degree. Twelve wavelength equalizers are used in the design—four for each degree. Wavelength equalizer WE1 1205 a is used to either pass or block wavelengths from the West Line interface 1201 a to the multiplexer/de-multiplexer circuit pack 1220. Similarly, wavelength equalizer WE5 1205 e and WE9 1205 i are used to either pass or block wavelengths from the East 1202 a and South 1203 a Line interfaces to the multiplexer/de-multiplexer circuit pack 1220. The wavelengths from WE1 1205 a, WE5 1205 e, and WE9 1205 i are combined together using optical coupler 1234, and then they are forwarded to the multiplexer/de-multiplexer circuit pack 1220 via optional optical amplifier 1242 through the common port 1270 a.

Wavelength equalizer WE4 1205 d is used to either pass or block wavelengths from the multiplexer/de-multiplexer circuit pack 1220 to the West Line interface 1201 b. It is also used to equalize the power levels of the wavelengths exiting out the West Line interface 1201 b rom the multiplexer/de-multiplexer circuit pack 1220. Similarly, wavelength equalizers WE8 1205 h and WE12 1205 m are used to either pass or block wavelengths from the multiplexer/de-multiplexer circuit pack 1220 to the East 1202 b and South 1203 b Line interfaces. They are also used to equalize the power levels of the wavelengths exiting out the East 1202 b and South 1203 b Line interfaces from the multiplexer/de-multiplexer circuit pack 1220.

Wavelength equalizer WE2 1205 b and WE3 1205 c are used to either pass or block wavelengths from the East 1202 a and South 1203 a Line interfaces to the West Line interface 1201 b. They are also used to equalize the power levels of the wavelengths exiting out the West Line interface 1201 b from the East 1202 a and South 1203 a Line interfaces. Similarly, wavelength equalizers WE6 1205 f and WE7 1205 g are used to either pass or block wavelengths from the West 1201 a and South 1203 a Line interfaces to the East Line interface 1202 b. They are also used to equalize the power levels of the wavelengths exiting out the East Line interface 1202 b from the West 1201 a and South 1203 a Line interfaces. Lastly, wavelength equalizers WE10 1205 j and WE11 1205 k are used to either pass or block wavelengths from the West 1201 a and East 1202 a Line interfaces to the South Line interface 1203 b. They are also used to equalize the power levels of the wavelengths exiting out the South Line interface 1203 b from the West 1201 a and East 1202 a Line interfaces.

Optional input optical amplifiers 1240 a-c are used to optically amplify wavelengths arriving from the West 1201 a, East 1202 a, and South 1203 a Line interfaces.

Optical coupler 1230 is used to broadcast all the wavelengths from the West Line interface 1201 a to wavelength equalizers WE1 1205 a, WE6 1205 f, and WE10 1205 j. Similarly, optical coupler 1232 is used to broadcast all the wavelengths from the East Line interface 1202 a to wavelength equalizer s WE2 1205 b, WE5 1205 e, and WE11 1205 k. Lastly, optical coupler 1236 is used to broadcast all the wavelengths from the South Line interface 1203 a to wavelength equalizers WE3 1205 c, WE7 1205 g, and WE9 1205 i.

Optical coupler 1231 is used to combine the wavelengths from wavelength equalizers WE2 1205 b, WE3 1205 c and WE4 1205 d into one composite WDM signal that is optically amplified with output optical amplifier 1241 a. Similarly, optical coupler 1233 is used to combine the wavelengths from wavelength equalizers WE6 1205 f, WE7 1205 g, and WE8 1205 h into one composite WDM signal that is optically amplified with output optical amplifier 1241 b. Lastly, optical coupler 1237 is used to combine the wavelengths from wavelength equalizers WE10 1205 j, WE11 1205 k, and WE12 1205 m into one composite WDM signal that is optically amplified with output optical amplifier 1241 c.

Optional optical amplifier 1243 receives added wavelengths from the multiplexer/de-multiplexer circuit pack 1220 via common port 1270 b, and optically amplifies the wavelengths before forwarding the amplified wavelengths to optical coupler 1235. Optical coupler 1235 is used to broadcast the added wavelengths to the West Line interface 1201 b, the East Line interface 1202 b, and the South Line Interface 1203 b via WE4 1205 d, WE8 1205 h, and WE12 1205 m respectively.

Located on the multiplexer/de-multiplexer circuit pack 1220 is a plurality (r) of add/drop ports 1260, 1261. Individual wavelengths are added to the multiplexer/de-multiplexer circuit pack and then multiplexed via multiplexer 1251 into a composite WDM signal that is then forwarded to the ROADM circuit pack 1210 via the common port 1270 b of the ROADM circuit pack. In the drop direction on 1220, a composite WDM signal is received from the ROADM circuit pack 1210 via the common port 1270 a and then it is de-multiplexed into individual wavelengths using de-multiplexer 1250. Each de-multiplexed wavelength is then forwarded to a specific drop port of the de-multiplexer. The multiplexer and de-multiplexer may be implemented using Arrayed Waveguide Grating (AWG) technology, or some other suitable technology. Devices that process individual wavelengths for transmission—such as optical transponders (not shown)—can be used to supply and receive wavelengths from the add/drop ports.

As can be seen in 1200, a single multiplexer/de-multiplexer circuit pack 1220 is used to add and drop wavelengths to/from the East, West, and South Line interfaces. Therefore, a transponder that is attached to an add/drop port of the multiplexer/de-multiplexer circuit pack 1220, can forward and receive wavelengths from any of the three degrees of the ROADM circuit pack. Because of this, the add/drop ports are referred to as directionless add/drop ports—meaning the add/drop ports are not dedicated to a particular direction of the optical node. The wavelength equalizers on the ROADM circuit pack are used to steer the added and dropped wavelengths to and from each degree by appropriately blocking or passing wavelengths. Therefore, the wavelength equalizers are said to perform directionless steering for the add/drop ports.

Additionally, the wavelength equalizers on the ROADM circuit pack are used to select which wavelengths from the Line input interfaces are allowed to exit a given output interface (degree), by appropriately blocking or passing wavelengths.

FIG. 13 shows a three-degree optical node 1300 that is identical to the optical node 1200, except that a single wavelength equalizing array 350 is used to supply all the required wavelength equalizers needed to construct the optical node. (Alternatively, multiple smaller wavelength equalizing arrays could be utilized.) The wavelength equalizers WE1-WE12 1305 a-m in 1300 correspond to the wavelength equalizers WE1-WE12 1205 a-m in 1200. The single wavelength equalizing array 350 may be identical to the wavelength equalizing array 350 discussed in reference to FIG. 3.

A single ROADM circuit pack 1310 supplies all the required optical circuitry to support three optical degrees, including input and output amplifiers for each degree, a common optical port connectable to a plurality of directionless add/drop ports, optical supervisory channel circuitry (not shown), optical channel monitoring (not shown), and a single wavelength equalizing array 350 that is used to both select wavelengths for each degree and to perform directionless steering for the add/drop ports of each degree.

As can be seen in 1300, a single multiplexer/de-multiplexer circuit pack 1320 is used to add and drop wavelengths to/from the East 1302 a-b, West 1301 a-b, and South 1303 a-b Line interfaces. Therefore, a transponder that is attached to an add/drop port of the multiplexer/de-multiplexer circuit pack 1320, can forward and receive wavelengths to/from any of the three degrees of the ROADM circuit pack. Because of this, the add/drop ports are referred to as directionless add/drop ports—meaning the add drop ports are not dedicated to a particular direction of the optical node. The wavelength equalizers on the ROADM circuit pack are used to steer the added and dropped wavelengths to and from each degree by appropriately blocking or passing wavelengths. Therefore, the wavelength equalizers are said to perform directionless steering for the add/drop ports.

Additionally, the wavelength equalizers on the ROADM circuit pack 1310 are used to select which wavelengths from the Line input interfaces are allowed to exit a given output Line interface (degree), by appropriately blocking or passing wavelengths.

The ROADM circuit pack 1310 is constructed on one or more printed circuit boards that are bound together electrically and mechanically so that the circuit pack can be plugged into a backplane as a single entity. The ROADM circuit pack additionally contains a front panel (used to house the optical connectors associated with the optical ports on the ROADM), electrical control circuitry (used to take in user commands needed to control the ROADM), power supply circuitry (used to provide the various voltage levels and electrical currents needed to power the various components on the ROADM), and one or more backplane connectors (needed to connect electrical signals on the ROADM circuit pack to signals on the back plane that the ROADM card is plugged into).

Alternatively, the optical multiplexer/de-multiplexer circuitry on the multiplexer/de-multiplexer circuit pack 1320 could be placed on the ROADM circuit pack 1310, thus eliminating a circuit pack in the optical node.

The add/drop ports on the multiplexer/de-multiplexer circuit pack 1320 are considered to be colored add/drop ports. This is because each add/drop port is used to support a particular optical frequency (wavelength). So therefore, add/drop port 1 will only support wavelength frequency 1, and therefore a transponder attached to add/drop port 1 must only generate wavelength frequency 1. An alternative (not shown) is to supply an alternative multiplexer/de-multiplexer circuit pack that contains colorless add/drop ports. A colorless add/drop port can be used to support any of the r wavelength frequencies associated with the ROADM circuit pack, and therefore a transponder attached to add/drop port 1 is allowed to generate any of the r wavelength frequencies.

The wavelength equalizing array (350) saves physical space and electrical power by utilizing common optics and electronics for all the wavelength equalizers in the array, thus making it more suitable for compact edge-of-network applications. The single wavelength equalizing array also provides a means to simplify the construction of the ROADM circuit pack that it is placed upon. Furthermore, the wavelength equalizing array 350 provides the flexibility to generate alternative functions and architectures by simply changing the manner in which the wavelength equalizing array is connected to other optical components on the ROADM circuit pack.

In summary, optical node 1300 comprises of three degrees with corresponding optical interfaces 1301 a-b, 1302 a-b, and 1303 a-b, a plurality of directionless add/drop ports 1361, 1360, and at least one wavelength equalizing array 350, wherein the at least one wavelength equalizing array 350 is used to both select wavelengths for each optical degree (via wavelength equalizers 1305 b-d, 1305 f-h, & 1305 j-m), and to perform directionless steering for the plurality of directionless add/drop ports 1361,1360 (via wavelength equalizers 1305 a, 1305 d, 1305 e, 1305 h, 1305 i, 1305 m). The three degree optical node may be implemented with a single ROADM circuit pack comprising of all three degrees.

FIG. 14 shows a three-degree optical node 1400 that is identical to the optical node 1200, except that a single wavelength equalizing array 800 is used to supply all the required wavelength equalizers needed to construct the optical node. The wavelength equalizing array that is used is the wavelength equalizing array 800 that was described in reference to FIG. 8. This wavelength equalizing array can be configured to perform the function of multiple 1 by 3 WSS functions. Therefore, the function of the optical couplers 1230, 1232, 1235, and 1236 of optical node 1200 are additionally absorbed within the wavelength equalizing array 800. The 3 by 1 WSS function 810 a performs the function of WE1 1205 a, WE6 1205 f, WE10 1205 j, and optical coupler 1230 within optical node 1200, while the 3 by 1 WSS function 810 b performs the function of WE3 1205 c, WE7 1205 g, WE9 1205 i, and optical coupler 1236 within optical node 1200, and the 3 by 1 WSS function 810 c performs the function of WE2 1205 b, WE5 1205 e, WE11 1205 k, and optical coupler 1232 within optical node 1200, and the 3 by 1 WSS function 810 d performs the function of WE4 1205 d, WE8 1205 h, WE12 1205 m, and optical coupler 1235 within optical node 1200. Couplers 1431, 1433, 1434, and 1437, correspond to the couplers 1231, 1233, 1234, and 1237 within ROADM circuit pack 1210. As can be seen from FIG. 14, using the wavelength equalizing array 800 in place of wavelength equalizing array 310 further simplifies the ROADM circuit pack due to the additional level of integration.

FIG. 15 shows an optical node 1500 comprising of a two-degree Reconfigurable Optical Add/Drop Multiplexer (ROADM) 1510 on a circuit pack with an external multiplexer/de-multiplexer circuit pack 1520. The ROADM circuit pack can be used as a stand-alone ROADM in a two degree node, or it can be paired with a second identical ROADM circuit pack in order to form a four degree node. The four Express ports (Express Out 1&2 and Express In 1&2 1560 a-d) are used to interconnect the two ROADMs when two ROADM circuit packs are paired to form a four-degree node. Each line interface on the ROADM (Line In/Out 1 1501 a-b and Line In/Out 2 1502 a-b) represents an optical degree. Ten wavelength equalizers 1505 a-j are used in the embodiment—five for each degree. Wavelength equalizer WE1 1505 a is used to either pass or block wavelengths from the Line1 interface 1501 a to the multiplexer/de-multiplexer circuit pack 1520. Similarly, wavelength equalizer WE6 1505 f is used to either pass or block wavelengths from the Line 2 interface 1502 a to the multiplexer/de-multiplexer circuit pack 1520. The wavelengths from WE1 1505 a and WE6 1505 f are combined together using optical coupler 1534, and then they are forwarded to the multiplexer/de-multiplexer circuit pack 1520 via optional optical amplifier 1542 through common optical port 1570 a.

Wavelength equalizer WE5 1505 e is used to either pass or block wavelengths from the multiplexer/de-multiplexer circuit pack 1520 to the Line 1 interface 1501 b. It is also used to equalize the power levels of the wavelengths exiting out the Line 1 interface 1501 b from the multiplexer/de-multiplexer circuit pack 1520. Similarly, wavelength equalizer WE10 1505 j is used to either pass or block wavelengths from the multiplexer/de-multiplexer circuit pack 1520 to Line 2 interface 1502 b. WE10 1505 j is also used to equalize the power levels of the wavelengths exiting out the Line 2 interface 1502 b from the multiplexer/de-multiplexer circuit pack 1520.

Wavelength equalizer WE2 1505 b, WE3 1505 c, and WE4 1505 d are used to either pass or block wavelengths from the Express 1560 b-c and Line 2 1502 a interfaces to the Line 1 interface 1501 b. They are also used to equalize the power levels of the wavelengths exiting out the Line 1 interface 1501 b from the Express 1560 b-c and Line 2 1502 a interfaces. Similarly, wavelength equalizers WE7 1505 g, WE8 1505 h, and WE9 1505 i are used to either pass or block wavelengths from the Line 1 1501 a and Express 1560 b-c interfaces to the Line 2 interface 1502 b. They are also used to equalize the power levels of the wavelengths exiting out the Line 2 1502 b interface from the Line 1 1501 a and Express 1560 b-c interfaces.

Optical couplers 1580 a and 1580 b are used to broadcast the Express In 1 1560 b and Express In 2 1560 c optical input signals to both the Line 1 1501 b and Line 2 1502 b interface directions.

Optional input optical amplifiers 1540 a-b are used to optically amplify wavelengths arriving from the Line 1 1501 a and 2 Line 2 1502 a interfaces.

Optical coupler 1530 is used to broadcast all the wavelengths from the Line 1 interface 1501 a to wavelength equalizers WE1 15050 a and WE7 1505 g, and the Express Out 1 port 1560 a. Similarly, optical coupler 1532 is used to broadcast all the wavelengths from the Line 2 interface 1502 a to wavelength equalizers WE2 1505 b and WE6 1505 f, and the Express Out 2 port 1560 d.

Optical coupler 1531 is used to combine the wavelengths from wavelength equalizers WE2 1505 b through WE5 1505 e into one composite WDM signal that is optically amplified with output optical amplifier 1541 a. Similarly, optical coupler 1533 is used to combine the wavelengths from wavelength equalizers WE7 1505 g through WE10 1505 j into one composite WDM signal that is optically amplified with output optical amplifier 1541 b.

Optional optical amplifier 1543 receives added wavelengths from the multiplexer/de-multiplexer circuit pack 1520 via common port 1570 b, and optically amplifies the wavelengths before forwarding the amplified wavelengths to optical coupler 1535. Optical coupler 1535 is used to broadcast the added wavelengths to the Line 1 interface 1501 b, and the Line 2 interface 1502 b via WE5 1505 e and WE10 1505 j respectively.

Located on the multiplexer/de-multiplexer circuit pack 1520 is a plurality (r) of add/drop ports 1561, 1560. Individual wavelengths are added to the multiplexer/de-multiplexer circuit pack and then multiplexed via multiplexer 1551 into a composite WDM signal that is then forwarded to the ROADM circuit pack 1510 via common port 1570 b. In the drop direction on 1520, a composite WDM signal is received from common port 1570 a of the ROADM circuit pack and then it is de-multiplexed into individual wavelengths using de-multiplexer 1550. Each de-multiplexed wavelength is then forwarded to a specific drop port of the de-multiplexer. The multiplexer and de-multiplexer may be implemented using Arrayed Waveguide Grating (AWG) technology, or some other suitable technology. Devices that process individual wavelengths for transmission—such as optical transponders—can be used to supply and receive wavelengths from the add/drop ports.

It should be noted that multiplexer/de-multiplexer circuit pack 1520 contains two WDM input ports (IN1 1575 b and IN2 1575 a), and two WDM output ports (OUT1 1575 d and OUT2 1575 c). This is to allow connection to up to two ROADM circuit packs 1510, as illustrated in FIG. 16A. An optical coupler 1555 is used combine composite WDM signals from two ROADM circuit packs 1510 before forwarding the composite WDM signal to de-multiplexer 1550. An optical coupler 1556 is used to broadcast the composite WDM signal from multiplexer 1551 to two ROADM circuit packs 1510.

As can be seen in 1500, a single multiplexer/de-multiplexer circuit pack 1520 is used to add and drop wavelengths to/from the Line 1 1501 a and Line 2 1502 a interfaces. Therefore, a transponder that is attached to an add/drop port of the multiplexer/de-multiplexer circuit pack 1520, can forward and receive wavelengths from either of the two degrees of the ROADM circuit pack. Because of this, the add/drop ports are referred to as directionless add/drop ports—meaning the add drop ports are not dedicated to a particular direction of the optical node. If two ROADM circuit packs 1510 a-b are paired to form a four-degree optical node (as shown in 1600 of FIG. 16A), wherein ROADM circuit packs 1510 a-b are identical to ROADM circuit pack 1510), the optical couplers 1555 and 1556 allow a transponder that is attached to an add/drop port of the multiplexer/de-multiplexer circuit pack 1520 to forward and receive wavelengths from any of the four degrees of the combined two ROADM circuit packs 1510 a and 1510 b. The wavelength equalizers (1505 a, 1505 e, 1505 f, and 1505 j) on the two ROADM circuit packs are used to steer the added and dropped wavelengths to and from each degree by appropriately blocking or passing wavelengths. Therefore, the wavelength equalizers are said to perform directionless steering for the add/drop ports.

Additionally, the wavelength equalizers (1505 b-e and 1505 g-j) on the two ROADM circuit packs 1510 a-b are used to select which wavelengths from the Line input interfaces and add ports are allowed to exit a given output interface (degree), by appropriately blocking or passing wavelengths.

FIG. 16A shows a four-degree optical node 1600. It uses two of the ROADM circuit packs 1510 a and 1510 b, and a single multiplexer/de-multiplexer circuit pack 1520. The single multiplexer/de-multiplexer circuit pack 1520 contains two WDM input ports (IN1 1575 b and IN2 1575 a), and two WDM output ports (OUT1 1575 d and OUT2 1575 c), allowing both the ROADM circuit packs to share a common set of transponders (attached to the add/drop ports on the multiplexer/de-multiplexer circuit pack). The common set of transponders can connect to any of the four degrees (East 1672 b, West 1672 a, North 1672 d, and South 1672 c). ROADM circuit Pack 1 1510 a sends all wavelengths it receives from its two line interfaces 1672 a-b to ROADM circuit Pack 2 1510 b via ROADM circuit Pack 1's two Express Out ports (1 & 2 1674 a-b). Similarly, ROADM circuit Pack 2 1510 b sends all wavelengths it receives from its two line interfaces 1672 c-d to ROADM circuit Pack 1 1510 a via ROADM circuit Pack 2's two Express Out ports (1 & 2 1678 a-b). The result is that both ROADM Circuit Pack 1 1510 a and Circuit Pack 2 1510 b have access to all wavelengths received from all four degrees of the optical node.

In 1600, Express OUT 1 1674 a, Express OUT2 1674 b, Express IN 1 1677 a, and Express IN 2 1677 b, correspond to the same signals Express OUT 1 1560 a, Express OUT2 1560 d, Express IN 1 1560 b, and Express IN 2 1560 c in 1500 respectively. Similarly, in 1600, Express OUT 1 1678 a, Express OUT2 1678 b, Express IN 1 1676 a, and Express IN 2 1676 b, correspond to the same signals Express OUT 1 1560 a, Express OUT2 1560 d, Express IN 1 1560 b, and Express IN 2 1560 c in 1500 respectively.

FIG. 16B shows a four-degree optical node 1650. It uses two of the ROADM circuit packs 1510 a-b, and two multiplexer/de-multiplexer circuit packs 1420 a-b. (Alternatively, it could also use multiplexer/de-multiplexer circuit packs 1520, and just use only one pair of IN/OUT ports.) Using two multiplexer/de-multiplexer circuit packs provides some added reliability. A drawback is that a given transponder attached to an add/drop port of one of the multiplexer/de-multiplexer circuit packs will only be able to communicate through the two optical degrees associated with the ROADM that the multiplexer/de-multiplexer circuit pack is attached to. So, in this case, the add/drop ports are directionless, but a given transponder is only able to send and receive wavelengths from two of the four degrees.

The two multiplexer/de-multiplexer circuit packs 1520, 1420 may contain active components (i.e., components requiring electrical power in order to operate), or they may contain only passive components (athermal AWGs, for example). If the multiplexer/de-multiplexer circuit packs contain only passive components, then the multiplexer/de-multiplexer circuit packs could optionally be placed outside of the electrical shelf that is holding the ROADM circuit packs.

FIG. 17 shows a two-degree optical node 1700 that is identical to the optical node 1500, except that a single wavelength equalizing array is used to supply all the required wavelength equalizers needed to construct the optical node. (Alternatively, multiple smaller wavelength equalizing arrays could be utilized.) The wavelength equalizers WE1-WE10 in 1700 correspond to the wavelength equalizers WE1-WE10 in 1500. The single wavelength equalizing array 310 may be identical to the wavelength equalizing array 310 discussed in reference to FIG. 3.

A single ROADM circuit pack 1710 supplies all the required optical circuitry to support two optical degrees, including input and output amplifiers for each degree, an optical common port connectable to a plurality of directionless add/drop ports, optical supervisory channel circuitry (not shown), optical channel monitoring (not shown), and a single wavelength equalizing array 310 that is used to both select wavelengths for each degree and to perform directionless steering for the add/drop ports.

The ROADM circuit pack can be used as a stand-alone ROADM in a two-degree node, or it can be paired with a second identical ROADM circuit pack in order to form a four-degree node. The four Express ports (Express Out 1&2 1760 ad and Express In 1&2 1760 b,c) are used to interconnect the two ROADMs in the same manner as shown in FIG. 16A.

As can be seen in 1700, a single multiplexer/de-multiplexer circuit pack 1720 is used to add and drop wavelengths to/from the Line 1 1701 a-b and Line 2 1702 a-b interfaces. Therefore, a transponder that is attached to an add/drop port of the multiplexer/de-multiplexer circuit pack 1720, can forward and receive wavelengths from either of the two degrees of the ROADM circuit pack. If a second ROADM circuit pack is added to the optical node, a transponder that is attached to an add/drop port of the multiplexer/de-multiplexer circuit pack 1720, can forward and receive wavelengths from any of the four degrees of the resulting optical node. The wavelength equalizers on the ROADM circuit pack are used to steer the added and dropped wavelengths to and from each degree by appropriately blocking or passing wavelengths. Therefore, the wavelength equalizers are said to perform directionless steering for the add/drop ports for each degree.

Additionally, the wavelength equalizers on the ROADM circuit pack 1710 are used to select which wavelengths from the Line input interfaces are allowed to exit a given output Line interface (degree), by appropriately blocking or passing wavelengths.

The ROADM circuit pack is constructed on one or more printed circuit boards that are bound together electrically and mechanically so that the circuit pack can be plugged into a backplane as a single entity. The ROADM circuit pack additionally contains a front panel (used to house the optical connectors associated with the optical ports on the ROADM), electrical control circuitry (used to take in user commands needed to control the ROADM), power supply circuitry (used to provide the various voltage levels and electrical currents needed to power the various components on the ROADM), and one or more backplane connectors (needed to connect electrical signals on the ROADM to signals on the back plane that the ROADM card is plugged into).

Alternatively, the optical multiplexer/de-multiplexer circuitry on the multiplexer/de-multiplexer circuit pack 1720 could be placed on the ROADM circuit pack 1710, thus eliminating a circuit pack in the optical node.

The add/drop ports on the multiplexer/de-multiplexer circuit pack 1720 are considered to be colored add/drop ports. This is because each add/drop port is used to support a particular optical frequency (wavelength). So therefore, add/drop port 1 will only support wavelength frequency 1, and therefore a transponder attached to add/drop port 1 must only generate wavelength frequency 1. An alternative (not shown) is to supply an alternative multiplexer/de-multiplexer circuit pack that contains colorless add/drop ports. A colorless add/drop port can be used to support any of the r wavelength frequencies associated with the ROADM circuit pack, and therefore a transponder attached to add/drop port 1 is allowed to generate any of the r wavelength frequencies.

The wavelength equalizing array saves physical space and electrical power by utilizing common optics and electronics for all the wavelength equalizers in the array, thus making it more suitable for compact edge-of-network applications. The single wavelength equalizing array also provides a means to simplify the construction of the ROADM circuit pack that it is placed upon.

In summary, this invention presents an embodiment of an optical node 1600 comprising of four optical degrees, and further comprising of a plurality of directionless add/drop ports 1561, 1560, and including a first circuit pack 1510 a and a second circuit pack 1510 b, wherein each circuit pack interfaces to at least two of the four optical degrees 1672 a-d. The node additionally contains at least one wavelength equalizing array 310. The optical node 1600 may further include a third circuit pack 1520/1720, containing the plurality of directionless add/drop ports 1561, 1560, and wherein the first and second circuit packs 1510 a-b direct wavelengths to and from the third circuit pack. The first and second circuit packs may be ROADM circuit packs, each comprising of a single wavelength equalizing array and a common port connectable to a plurality of directionless add/drop ports, wherein each ROADM circuit pack interfaces to at least two of the four optical degrees, and wherein each wavelength equalizing array is used to both select wavelengths for the optical degrees and to perform directionless steering for the plurality of directionless add/drop ports.

FIG. 18 shows a two-degree optical node 1800 that is identical to the optical node 1500, except that a single wavelength equalizing array 600 is used to supply all the required wavelength equalizers needed to construct the optical node. The wavelength equalizing array that is used is the wavelength equalizing array that was described in reference to FIG. 6. This wavelength equalizing array can be configured to perform the function of multiple 1 by 2 WSS functions. Therefore, the function of the optical coupler 1534 of optical node 1500 is additionally absorbed within the wavelength equalizing array 600. Also, the functions of optical couplers 1531 and 1533 are partially absorbed within the array 600 in 1800. The 2 by 1 WSS function 1840 a performs the function of WE1 1505 a, WE6 1505 f, and optical coupler 1534 within optical node 1500, while the 2 by 1 WSS function 1840 b performs the function of WE2 1505 b, WE3 1505 c, and partially optical coupler 1531 within optical node 1500, and the 2 by 1 WSS function 1840 c performs the function of WE7 1505 g, WE8 1505 h, and partially optical coupler 1533 within optical node 1500, and the 2 by 1 WSS function 1840 d performs the function of WE4 1505 d, WE5 1505 e, and partially optical coupler 1531 within optical node 1500, and the 2 by 1 WSS function 1840 e performs the function of WE9 1505 i, WE10 1505 j, and partially optical coupler 1533 within optical node 1500. As can be seen from the figure, using the wavelength equalizing array 600 in place of wavelength equalizing array 310 further simplifies the ROADM circuit pack due to its additional level of integration.

Although a wavelength equalizing array of 2 by 1 WSS functions was utilized to build ROADM circuit pack 1800, a wavelength equalizing array that can be configured for either 4 by 1 WSS functions or 2 by 1 WSS functions could be used instead, in order to eliminate additional circuitry. For instance, a first 4 by 1 WSS could absorb WE2 1505 b, WE3 1505 c, WE4 1505 d, WE5 1505 e, and coupler 1531 on the ROADM circuit pack 1500. Similarly, a second 4 by 1 WSS could absorb WE7 1505 g, WE8 1505 h, WE9 1505 i, WE10 1505 j, and coupler 1533 on the ROADM circuit pack 1500. A 2 by 1 WSS could absorb WE1 1505 a, WE6 1505 f, and coupler 1534 on the ROADM circuit pack 1500. Therefore, different ROADM circuit packs can be constructed such that they are built using a single wavelength equalizing array wherein different size WSS functions are utilized within the array.

In general, an optical node or ROADM circuit pack could be constructed using a wavelength equalizing array that can be partitioned into an array of k₁ 1×1, k₂ 1×2, k₃ 1×3 . . . , k_(p) 1×p wavelength selective switches, where p is any integer number greater than 1, and k_(j) is any integer value greater than or equal to 0. A single type of wavelength equalizing array could be used to build different types of ROADM circuit packs. For instance, wavelength equalizing array 350 (FIG. 3) could be used to build a two-degree ROADM circuit pack 1010, a three-degree ROADM circuit pack 1310, or a four-degree capable ROADM circuit pack 1710. Similarly, wavelength equalizing array 800 (FIG. 8) could be used to build a two-degree ROADM circuit pack 1110, a three-degree ROADM circuit pack 1410, or a four-degree capable ROADM circuit pack 1810.

Although in 1800 two ROADM circuit packs are required to construct a four-degree optical node, all four degrees can be placed on a single ROADM circuit pack. In order to build the four degree ROADM using a single ROADM circuit pack, a wavelength equalizing array of 20 wavelength equalizers would be required—five for each of the four degrees. Alternatively, two wavelength equalizers with 10 wavelength equalizers each could be used.

Additionally, optical nodes containing greater than four degrees could be constructed by extending the concepts used to construct the three and four degree nodes.

FIG. 19 shows a two-degree optical node 1900 that is identical to the optical node 1700, except that two-additional wavelength equalizing arrays 1990 a-b are used to support optical channel monitor functions. As shown in FIG. 19, an additional 1 to 2 coupler 1991 & 1992 has been added after the output of each of the two output amplifiers within ROADM circuit pack 1910. The couplers are used to send a portion of the light from each output amplifier to the wavelength equalizers 1990 a-b. Operationally, each of the two newly added wavelength equalizers 1990 a-b are used to cycle through all r wavelengths exiting the two line interfaces in order to measure the optical power of each wavelength using photo diodes 1994 a-b.

FIG. 20 shows a two-degree optical node 2000 that is similar to the optical node 1000, except that u−6 internal transponders 2057 a-b are integrated in the ROADM circuit pack 2010 (wherein u may be any integer value greater than six). A wavelength equalizing array 380 with u wavelength equalizers is used. Each additional wavelength equalizer beyond six is used to filter out a single wavelength that is then dropped to an integrated transponder. Four optical couplers 2046-2049 are added to the node of 1000. Coupler 2048 is a (u−6):1 coupler used to combine the output wavelengths from the u−6 internal transponders. Coupler 2047 is used to combine the wavelengths from the internal transponders with the wavelengths from the multiplexer (via common port 2070 b) within the multiplexer/de-multiplexer circuit pack 2020. An optical amplifier (not shown) could optionally be placed at the output of optical coupler 2047. Optical coupler 2035 is then used to broadcast the wavelengths from the internal transponders and from the multiplexer/de-multiplexer circuit pack to both degrees—allowing the wavelengths from the internal transponders to be directionless.

In the drop direction, new coupler 2046 is used to broadcast all the dropped wavelengths received from both degrees to both the multiplexer/de-multiplexer circuit pack (via common port 2070 a) and to coupler 2049. Coupler 2049 is a 1:(u−6) coupler used to broadcast all the dropped wavelengths received from both degrees to the u−6 wavelength equalizers that are used to filter wavelengths for the u−6 internal transponders.

A ROADM circuit pack with integrated transponders 2010 allows for especially compact optical nodes, as no external transponders are required for cases where a small number of wavelengths are added and dropped.

FIG. 21 shows a three-degree optical node 2100 that is similar to the optical node 1300, except that u−12 internal transponders are integrated in the ROADM circuit pack 2110 (wherein u may be any integer value greater than twelve). A wavelength equalizing array 380 with u wavelength equalizers is used. Each additional wavelength equalizer beyond twelve is used to filter out a single wavelength that is then dropped to an integrated transponder. Four optical couplers 2146-2149 are added to the node of 1300. Coupler 2148 is a (u−12):1 coupler used to combine the output wavelengths from the u−12 internal transponders 2157 a-b. Coupler 2147 is used to combine the wavelengths from the internal transponders with the wavelengths from the multiplexer within the multiplexer/de-multiplexer circuit pack 2120. An optical amplifier is optionally placed at the output of optical coupler 2147. Optical coupler 2135 is then used to broadcast the wavelengths from the internal transponders and from the multiplexer/de-multiplexer circuit pack to all three degrees—allowing the wavelengths from the internal transponders to be directionless.

In the drop direction, new coupler 2146 is used to broadcast all the dropped wavelengths received from all three degrees to both the multiplexer/de-multiplexer circuit pack 2120 (via common port 2170 a) and to coupler 2149. Coupler 2149 is a 1:(u−12) coupler used to broadcast all the dropped wavelengths received from all three degrees to the u−12 wavelength equalizers that are used to filter wavelengths for the u−12 internal transponders.

FIG. 22 shows an expandable (to four degrees) two-degree optical node 2200 that is similar to the optical node 1700, except that u−10 internal transponders are integrated in the ROADM circuit pack 2210 (wherein u may be any integer value greater than ten). A wavelength equalizing array 380 with u wavelength equalizers is used. Each additional wavelength equalizer beyond ten is used to filter out a single wavelength that is then dropped to an integrated transponder. Four optical couplers 2246-2249 are added to the node of 1700. Coupler 2248 is a (u−10):1 coupler used to combine the output wavelengths from the u−10 internal transponders. Coupler 2247 is used to combine the wavelengths from the internal transponders with the wavelengths from the multiplexer within the multiplexer/de-multiplexer circuit pack 2220. An optical amplifier is optionally placed at the output of optical coupler 2247. Optical coupler 2235 is then used to broadcast the wavelengths from the internal transponders and from the multiplexer/de-multiplexer circuit pack to both degrees on the circuit pack—allowing the wavelengths from the internal transponders to be directionless with respect to the two degrees on the circuit pack.

In the drop direction, new coupler 2246 is used to broadcast all the dropped wavelengths received from both degrees on the circuit pack to both the multiplexer/de-multiplexer circuit pack (via common port 2270 a) and to coupler 2249. Coupler 2249 is a 1:(u−10) coupler used to broadcast all the dropped wavelengths received from both degrees to the u−10 wavelength equalizers that are used to filter wavelengths for the u−10 internal transponders.

A drawback of the optical node 2200 is that the u−10 internal transponders can only send to and receive from the two degrees of the circuit pack that they reside on. Optical node 2300 in FIG. 23 overcomes this limitation. The u−12 internal transponders 2357 a-b within ROADM circuit pack 2310 can send and receive to and from any of the four degrees when two ROADM circuit packs 2310 are paired together to form a four degree node. This is accomplished by using an additional four-fiber interconnection between the two paired ROADM circuit packs. In FIG. 23 the four additional signals that are passed between the two ROADM circuit packs are labeled: Internal Add Out 2380 a, Internal Add In 2380 d, Internal Drop Out 2380 c, and Internal Drop In 2380 b. Four optical couplers are added to the ROADM circuit pack 2210: 2375-2378. Coupler 2375 is used to broadcast the composite signal from coupler 2348 containing the generated wavelengths from all u−12 internal transponders to both optical coupler 2376 and Wavelength Equalizer WE11 (2305 a). Wavelength Equalizer WE11 (2305 a) is used to block or pass any of the internally generated wavelengths to the paired ROADM circuit pack (the second ROADM circuit pack). This is a useful feature if an internally generated wavelength of a particular frequency is already being injected on the paired ROADM circuit pack. The output of WE11 (2305 a) is sent to the optical connector labeled Internal Add Out 2380 a on the first ROADM circuit pack. Internal Add Out 2380 a on the first ROADM circuit pack is connected to Internal Add In on the second ROADM circuit pack via an optical jumper, and vice versa. The wavelengths arriving on the optical connector labeled Internal Add In on the second ROADM circuit pack are forwarded to the optical coupler 2376 on the second ROADM circuit pack, where they are combined with the internal generated wavelengths of the second circuit pack. Therefore, the signal exiting coupler 2376 contains the internally generated wavelengths of the second ROADM circuit pack, and any internally generated wavelengths from the first ROADM circuit pack that will be forwarded to at least one of the two degrees of the second ROADM circuit pack. All of these wavelengths are then combined with the wavelengths from the multiplexer/de-multiplexer circuit pack 2320 using optical coupler 2347. The resulting signals are optionally amplified by the ADD Amp 2211, and then broadcasted to both WE10 (2305 b) and WE5 (2305 c). WE10 (2305 b) is used to pass or block wavelengths to Line Out 2 (2302 b), while WE5 (2305 c) is used to pass or block wavelengths to Line Out 1 (2301 b). Therefore, it can be seen that internally generated wavelengths from the first ROADM circuit pack can be forwarded to both degrees of the paired second ROADM circuit pack.

In the drop direction, wavelengths to be dropped from the Line In 1 (2301 a) and Line In 2 (2302 a) interfaces on the first ROADM circuit pack are selected via WE1 (2305 d) and WE6 (2305 e). These two sets of wavelengths to be dropped are combined using coupler 2334. The composite WDM signal from 2334 is broadcasted to optical coupler 2378 and the optical connector labeled Internal Drop Out 2380 c using optical coupler 2377. All of the dropped signals from the first ROADM circuit pack are sent to the second ROADM circuit pack via the optical connector labeled Internal Drop Out 2380 c on the first ROADM circuit pack. The optical connector labeled Internal Drop Out 2380 c on the first ROADM circuit pack is connected to the optical connector labeled Internal Drop In on the second ROADM circuit pack using an optical jumper. Therefore, all the dropped wavelengths from the first ROADM circuit pack are made available to the second ROADM circuit pack via the connector labeled Internal Drop In on the second ROADM circuit pack. The wavelengths arriving on the connector labeled Internal Drop In on the second ROADM circuit pack are forwarded to Wavelength Equalizer WE12 (2305 f) on the second circuit pack. WE12 (2305 f) can be used to block any wavelengths that are not being dropped on the second ROADM circuit pack. Typically, WE12 (2305 f) should block all wavelengths other than the wavelengths destined for internal transponders on the second ROADM circuit pack. The wavelengths that are not blocked by WE12 (2305 f) are combined with the wavelengths being dropped from the Line 1 (2301 a) and Line 2 (2302 a) interfaces on the second ROADM circuit pack using coupler 2378 on the second ROADM circuit pack. The combined signals are optionally amplified by the Drop Amp 2312 on the second ROADM circuit pack, and then broadcasted to both the multiplexer/de-multiplexer circuit pack 2320 and optical coupler 2349 via coupler 2346. Coupler 2349 broadcasts its inputted signal to the entire group of the u−12 Wavelength Equalizers used to filter out individual drop wavelengths for the internal transponders on the second ROADM circuit pack. In this manner, wavelengths dropped from any of the four degrees in a four-degree node can be forwarded to any internal transponder on either of the two paired ROADM circuit packs (assuming all wavelength blocking is accounted for). The two wavelength equalizers WE11 (2305 a) and WE12 (2305 f) can be used to isolate the add/drop signals associated with the paired ROADM circuit packs.

The optical node 2400 with wavelength equalizing array 350 shown in FIG. 24 is an alternative to optical node 2300. In the optical node 2400, the internal transponders can send and receive wavelengths from any of the four degrees when a four-degree node is created using two of the ROADM circuit packs 2410, but instead of the internal transponders being located within the ROADM circuit packs they are instead located within the multiplexer/de-multiplex circuit pack 2420. This greatly simplifies the design, but a separate wavelength equalizing array 380 is now required in the node for the multiplexer/de-multiplex circuit pack. In the add direction, the output from u number of transponders are combined using optical coupler 2448. The composite WDM signal from coupler 2448 is then combined with the composite WDM signal from the multiplexer (MUX) via coupler 2447. The resulting signal is optionally amplified by the Add Amp 2411, and then broadcasted to both ROADM circuit packs (only one shown) attached to the multiplexer/de-multiplex circuit pack 2420. In this manner, any signal generated by the transponders internal to the multiplexer/de-multiplex circuit pack 2420 are able to be inserted into either of the two degrees on the two ROADM circuit packs (via WE5 (2405 b) and WE10 (2405 a)).

In the drop direction, wavelengths being dropped from both Line In 1 (2401 a) and Line In 2 (2402 a) on a given ROADM circuit pack are combined using coupler 2434, and then forwarded to the multiplexer/de-multiplex circuit pack 2420. Coupler 2495 is then used to combine dropped signals from both ROADM circuit packs into one composite WDM signal that is amplified by the Drop Amp 2412 and then broadcasted to both the DMUX and optical coupler 2449 via coupler 2446. Coupler 2449 is used to broadcast all of the dropped channels from both ROADM circuit packs to all of the u wavelength equalizers within the wavelength equalizing array 380. Each of the u wavelength equalizers is used to select a single wavelength for its corresponding internal transponder 2457 a-u. Therefore, in this manner, each of the u internal transponders has access to all of the dropped wavelengths associated with all four degrees.

Although only a single common optical port is shown on the ROADM circuit packs of the optical nodes 1000, 1300, 1700, 1900, 2000, 2100, 2200, 2300, 2400, and 2500, the invention is not limited to a single common port on a given ROADM circuit pack, and in fact, a given ROADM circuit pack may contain any number of common ports C. Each common port requires two wavelength equalizers per degree, with one of the two wavelength equalizers being used in the drop direction, and with one of the two wavelength equalizers being used in the add direction—each wavelength equalizer being used in the same manner as was shown for the ROADM circuit packs containing only a single common port.

In order to provide additional flexibility and reliability, the optical amplifiers within an optical node may be pluggable into the front panel of a ROADM circuit pack, as illustrated in FIG. 25 and FIG. 26. FIG. 25 2500 shows a ROADM circuit pack 2510 with wavelength equalizing array 200 with five front panel pluggable amplifiers 2501 a-e. There are four pluggable amplifiers 2501 a-d containing a single EDFA 2502 a-d, and one pluggable amplifier containing two EDFAs 2501 e. Each pluggable amplifier may contain the amplifying EDFA and other electrical and optical components (not shown). Each pluggable amplifier may further comprise of an electrical connector (not shown), used to apply electrical power to the amplifier, as well as control signals to control the amplifier and retrieve status information from the amplifier. Each pluggable amplifier may additionally comprise of an optical connector 2506 a-f used to attach an external optical transmission fiber, and an optical connector 2503 a-f used to optically jumper 2504 a-f the associated amplifier to other optical circuitry 2530-2535 within the ROADM circuit pack via optical connector 2505 a-f. Optionally, the optical jumper 2504 a-f could be replaced by a blind-mate optical connector on the pluggable amplifier.

FIG. 26 (2600) shows a three-dimensional view of the ROADM circuit pack 2610 that can accommodate the five pluggable amplifiers 2501 a-e shown in 2500. FIG. 26 shows three pluggable amplifiers 2601 a-c (each comprising of a single EDFA) plugged into the front panel 2650 of the ROADM circuit pack 2610. FIG. 26 also shows a pluggable amplifier 2601 e (comprising of a two EDFAs) plugged into the front panel 2650 of the ROADM circuit pack 2610. Additionally, FIG. 26 shows a fifth pluggable amplifier 2601 d external to the ROADM circuit pack. Pluggable amplifier 2601 d may be plugged into slot 2630 on the front panel 2650 of the ROADM circuit pack 2610. Each of the pluggable circuit packs 2601 a-d containing a single EDFA also comprises of an optical connector 2606 a-d to attach an external optical transmission fiber, and an optical connector 2603 a-d used to optically jumper the associated amplifier to other optical circuitry within the ROADM circuit pack via optical connectors 2605 a-d contained on the front panel 2650 of the ROADM circuit pack 2610. The pluggable circuit pack 2601 e containing a two EDFAs also comprises of optical connectors 2606 e-f to attach external optical transmission fibers, and an optical connector 2603 e-f used to optically jumper the associated amplifier to other optical circuitry within the ROADM circuit pack via optical connectors 2605 e-f contained on the front panel 2650 of the ROADM circuit pack 2610. The optical jumper used to connect the pluggable amplifier to the other optical circuitry within the ROADM circuit pack may comprise of a substantially flat planer lightwave circuit with optical connectors 2680, or it may comprise of some alternative optical connection technology (such as a simple short optical cable). The jumper 2680 could be further fastened to the front panel 2650 using some mechanical means such as mechanical screws 2690 a-b.

FIG. 27 illustrates a process 2700 of constructing a multi-degree optical node utilizing a wavelength equalizing array. At block 2701, the number of degrees N for the optical node is selected. At block 2705, the number of ports C common to all degrees is selected. At Step 2710, a set of N−1+C wavelength equalizers is allocated for the purpose of transmission of wavelengths from the first optical degree. At block 2715, a decision is made: if there are additional optical degrees, the process returns to block 2710, where an additional set of N−1+C wavelength equalizers is allocated for each additional degree. Once all N degrees have a set of N−1+C wavelength equalizers allocated to them, the process proceeds to block 2720. At this point, the total number of wavelength equalizers allocated is: N×(N−1+C). At block 2720, it is determined if there is at least one common optical port within the multi-degree optical node. If there are no common ports, the process proceeds to block 2730. If there is at least one common port, then the process proceeds to block 2725. At block 2725, for each common port, a set of N wavelength equalizers is allocated for transmission of a set of wavelengths from each common port. The number of wavelength equalizers allocated at this block is: C×N. Once the wavelength equalizers have been allocated for the common ports, the process proceeds to block 2730. At block 2730, it is determined if there are any optical channel monitors. If there are no optical channel monitors, then the process proceeds to block 2740. If there is at least one optical channel monitor, then at block 2735, M number of wavelength equalizers are allocated for M number of optical channel monitors. It should be noted that two or more optical degrees may share a single optical channel monitor by switching the optical channel monitor between the two or more optical degrees. Once the M wavelength equalizers have been allocated, the process proceeds to block 2740. At block 2740, it is determined if there are any embedded transponders. If there are no embedded optical transponders, then the process ends. If there is at least one embedded transponder, then at block 2745, T number of wavelength equalizers are allocated for T number of embedded transponders. Once, the T number of wavelength equalizers have been allocated at block 2745 the process ends. When the process 2700 ends, the total number of wavelength equalizers allocated to the optical node is: N×(N−1+C)+(C×N)+M+T, which is equal to N²+N(2C−1)+M+T. For the special case where C=1, the total number of wavelength equalizers allocated is equal to: N²+N+M+T.

Based upon the process presented in 2700, it is seen that the invention provides for a method of constructing a multi-degree optical node utilizing a wavelength equalizing array, comprising of allocating a first set of wavelength equalizers 2710 for selection of a first set of wavelengths for transmission from a first optical degree, and allocating at least a second set of wavelength equalizers 2710 for selection of at least a second set of wavelengths for transmission from at least a second optical degree, wherein the number of optical degrees N comprising the node is used to determine the number of wavelength equalizers assigned to each set. The method further includes allocating an additional set of wavelength equalizers 2725 for selection of an additional set of wavelengths for transmission from a common port connectable to a plurality of directionless add/drop ports. The method further includes allocating at least one wavelength equalizer 2735 for selection of wavelengths for an optical channel monitor. The method also further includes allocating at least one wavelength equalizer 2745 for selection of a wavelength for at least one transponder.

FIG. 28 is an illustration of an optical node 2800 comprising of ROADM circuit pack 2810, a multiplexer/de-multiplexer circuit pack 2020, and a plurality of transponders 2857 ab that are external to the ROADM circuit pack 2810 and the optical multiplexer/de-multiplexer circuit pack 2020. The ROADM circuit pack comprises: a first optical degree 2801 ab, a second optical degree 2802 ab, a single common optical port 2070 ab, a plurality of embedded add/drop ports 2806 ab, 2804 ab, a plurality of optical amplifiers (EDFAs), a plurality of optical couplers (1:2, 2:1, u−6:1, 1:u−6), and a wavelength equalizing Array 380 having u number of wavelength equalizers. The optical multiplexer/de-multiplexer circuit pack 2020 comprises: a de-multiplexer input port 2821 a connected to the drop connector 2070 a of the ROADM common port using optical jumper cable 972 a, a multiplexer output port 2821 b connected to the add connector 2070 b of the ROADM common port using optical jumper cable 972 b, a plurality of drop ports 2823 ab, a plurality of add ports 2824 ab, an optical wavelength de-multiplexer 2850, and an optical wavelength multiplexer 2851. The plurality of transponders 2857 ab are connected to the embedded add/drop ports 2806 ab, 2804 ab using optical jumpers 2872 ab, 2873 ab.

For a wavelength equalizing array 380 having u wavelength equalizers, the ROADM circuit pack 2810 is operable to support up to u−6 embedded add/drop ports 2806 ab, 2804 ab. This is because six (6) wavelength equalizers are needed to pass and block wavelengths between the two optical degrees and the common port of the ROADM circuit pack. Since the ROADM circuit pack 2810 supports u−6 embedded add/drop ports, up to u−6 external transponders 2857 ab can be attached to the ROADM circuit pack via the embedded add/drop ports 2806 ab,2804 ab.

The optical transmitter ports 2808 ab of the transponders 2857 ab are connected to the add ports 2806 a-b of the ROADM circuit card 2810 using optical jumpers 2872 ab. Each transponder 2857 ab generates one optical wavelength. Each transponder 2857 ab generates an optical wavelength that differs in frequency from the wavelength generated by all other transponders 2857 ab. The plurality of wavelengths generated by the transponders 2857 ab are optically combined with one another using optical coupler 2048, which is a u−6 to 1 optical coupler. The wavelengths from the optical coupler 2048 are combined with the added wavelengths from the add connector 2070 b of the common port using two to one (2:1) optical coupler 2047. The optical signal containing the wavelengths generated by the transponders 2857 ab and the added wavelengths from the multiplexer/de-multiplexer circuit pack 2020 are optionally amplified and then forwarded to optical coupler 2035, which broadcasts the wavelengths to wavelength equalizers WE6 and WE3 which can be programmed to pass and block the added wavelengths to both the West optical degree 2801 b and the East optical degree 2802 b. Therefore, it can be seen that the embedded add ports 2806 ab are directionless add ports, as their wavelengths can be forwarded to either optical degree of the ROADM circuit pack 2810.

Optical wavelengths received at the first (West) optical degree 2801 a are broadcasted to both wavelength equalizer WE1 and wavelength equalizer WE5. WE5 is used to pass and pass and block wavelengths from first optical degree 2801 a to the second optical degree 2802 b, while WE1 is used to pass and block wavelengths from the first optical degree 2801 a to the common port 2070 a and to the embedded drop ports 2804 ab. Optical wavelengths received at the second (East) optical degree 2802 a are broadcasted to both wavelength equalizer WE2 and wavelength equalizer WE4. WE2 is used to pass and pass and block wavelengths from second optical degree 2802 a to the first optical degree 2801 b, while WE4 is used to pass and block wavelengths from the second optical degree 2802 a to the common port 2070 a and to the embedded drop ports 2804 ab. Optical coupler 2034 is used to combine the wavelengths from WE1 and WE4, and forwards them to coupler 2046, which in turn broadcasts the wavelengths to be dropped to both multiplexer/de-multiplexer circuit pack 2020 and to optical coupler 2049. Optical coupler 2049 is a 1 to u−6 optical coupler used to broadcast the wavelengths to be dropped to wavelength equalizers WE7 to WEu. Wavelength equalizers WE7 to WEu are used to select individual wavelengths for the optical receivers of external transponders 2857 ab. The optical receivers of transponders 2857 ab are broadband receivers, and therefore, only one wavelength must be sent to each optical receiver. Each wavelength equalizer WE7 to WEu is programmed to pass a single wavelength, while blocking all other wavelengths. Since optical wavelengths from either the first optical degree 2801 a or the second optical degree 2802 a can be forwarded to any of the embedded drop ports 2804 ab, the embedded drop ports 2804 ab are directionless drop ports.

Additional wavelengths may be added by additional transponders (not shown) attached to the add ports of the multiplexer/de-multiplexer circuit pack 2020. Additional wavelengths may be dropped to additional transponders (not shown) attached to the drop ports of the multiplexer/de-multiplexer circuit pack 2020.

FIG. 29 is an illustration of an optical node 2900 that is similar to optical node 2800 (of FIG. 28), except that the ROADM circuit pack 2910 of 2900 contains an embedded optical transmitter/receiver 2959. The embedded optical transmitter/receiver 2959 may include the optical and electrical circuitry to serve as a fully functional transponder (making it identical to external transponders 2857 ab), or it may simply contain the electrical circuitry required to generate and receive a test signal. The embedded optical transmitter/receiver 2959 is a directionless embedded optical transmitter/receiver, since a wavelength from either the first optical degree 2801 a or the second optical degree 2802 a is able to be forwarded to the embedded optical transmitter/receiver 2959, and the embedded optical transmitter/receiver 2959 can generate an optical wavelength to either the first optical degree 2801 b or the second optical degree 2802 b.

The optical wavelength generated by the embedded optical transmitter/receiver 2959 is combined with the optical wavelengths generated by the external transponders 2857 ab using optical coupler 2961. These combined wavelengths are additionally combined with any wavelengths from the multiplexer/de-multiplexer circuit pack 2020 using optical coupler 2047, and the resulting combined added wavelengths are broadcasted to wavelength equalizers WE3 and WE6 (using coupler 2035), which are used to pass and block the added wavelengths to the first optical degree 2801 b and the second optical degree 2802 b. Additional wavelengths may be added by additional transponders (not shown) attached to the add ports of the multiplexer/de-multiplexer circuit pack 2020.

Wavelengths to drop from the first optical degree 2801 a and the second optical degree 2802 a are combined using optical coupler 2034, and the combined wavelengths to drop are sent to both the multiplexer/de-multiplexer circuit pack 2020 and the optical coupler 2949. Optical coupler 2949 is a 1 to u−6 optical coupler, and it is used to broadcast the wavelengths to drop to wavelength equalizers WE7 to WEu. Wavelength equalizer WE7 is used to select a wavelength for the embedded (internal) optical transmitter/receiver 2959, while wavelength equalizers WE8 to WEu are used to select wavelengths for the external transponders 2857 ab. Additional wavelengths may be dropped to additional transponders (not shown) attached to the drop ports of the multiplexer/de-multiplexer circuit pack 2020.

FIG. 30 is an illustration of an optical node 3000 that is similar to optical node 2900 (of FIG. 29), except that the ROADM circuit pack 3010 of 3000 has only a single embedded add/drop port 2806,2804, although it is not limited to only a single embedded add/drop port. Also, both the embedded (internal) optical transmitter/receiver 2959 and the external transponder 2857 have their transmitted signals filtered by wavelength equalizers WE10 3041 and WE9 3040 respectively. Such filtering may be desired for cases where the sidemode suppression ratios of the lasers within the embedded optical transmitter/receiver 2959 and the external transponder 2857 are low.

As can be seen in FIG. 30, the output wavelength generated by the embedded optical transmitter/receiver 2959 is sent to WE10 3041, which is programmed to only pass the wavelength frequency generated by the embedded optical transmitter/receiver 2959. Similarly, the output wavelength generated by the external transponder 2857 is sent to WE9 3040, which is programmed to only pass the wavelength frequency generated by the external transponder 2857. The filtered outputs of WE9 and WE10 are then combined by optical coupler 2948, and the resulting signal is combined with any added wavelengths from the multiplexer/de-multiplexer circuit pack 2020 using optical coupler 2047. The added wavelengths from the optical coupler 2047 are broadcasted to both WE3 and WE6, which are used to pass and block added wavelengths to both the first optical degree 2801 b and the second optical degree 2802 b. Therefore, all added wavelengths are directionless.

In the drop direction, optical coupler 2034 is used to combine wavelengths from both the first optical degree 2801 a and the second optical degree 2802 a, and the resulting signal is broadcasted to both the multiplexer/de-multiplexer circuit pack 2020 and the optical coupler 3049. Optical coupler 3049 is used to broadcast the wavelengths to be dropped to WE7 3038 and WE8 3039, which are each programmed to select a single wavelength. WE7 3038 is used to select a single wavelength for the external optical transponder 2857, and WE8 3039 is used to select a single wavelength for the embedded optical transmitter/receiver 2959.

FIG. 31 is an illustration of a two-degree optical node 3100 comprised of two ROADMs 3110 a and 3110 b. The first ROADM 3110 a comprises: a first degree 3101 ab, a degree express port 3101 k 1, an add express port 3101 ij, two embedded add ports 3101 cd, an add expansion port 3101 e, two embedded drop ports 3101 fg, a drop expansion port 3101 h, a degree input amplifier 3140 a, a degree output amplifier 3141 a, a 3 by 1 WSS device 3160 a, a 2 by 1 WSS device 3161 a, a 1 by 2 WSS device 3162 a, optical couplers 3130 a-d, and optical couplers 3131 ab. Similarly the second ROADM 3110 b comprises: a second degree 3102 ab, a degree express port 3102 k 1, an add express port 3102 ij, two embedded add ports 3102 cd, an add expansion port 3102 e, two embedded drop ports 3102 fg, a drop expansion port 3102 h, a degree input amplifier 3140 b, a degree output amplifier 3141 b, a 3 by 1 WSS device 3160 b, a 2 by 1 WSS device 3161 b, a 1 by 2 WSS device 3162 b, optical couplers 3130 e-h, and optical couplers 3131 cd.

The degree express port 3101 k 1 is connected to the degree express port 3102 k 1 using optical jumper cables 3190 ab. The add express port 3101 ij is connected to the add express port 3102 ij using optical jumper cables 3190 cd.

On ROADM 3110 a, optical coupler 3131 b is used to combine individual wavelengths applied to the embedded add ports 3101 cd. The transmitter outputs of two transponders may be attached to embedded add ports 3101 cd. The add expansion port 3101 e may be attached to an optical multiplexer/de-multiplexer circuit pack such as 2020 in FIG. 30. Optical coupler 3131 a is used to combine the optical wavelengths from optical coupler 3131 b with the optical wavelengths received at the add expansion port 3101 e, and the combined wavelengths are broadcasted to both 3 by 1 WSS 3160 a and the add express port 3101 i. The optical coupler 3130 b is used to broadcast wavelengths received from the degree express port 3101 k to both the 3 by 1 WSS 3160 a and the 2 by 1 WSS 3161 a. The add express port 3101 j forwards added wavelengths from ROADM 3110 b to the 3 by 1 WSS 3160 a. The 3 by 1 WSS 3160 a is used to pass and block wavelengths from the embedded add ports 3101 cd, the add expansion port 3101 e, the degree express port 3101 k, and the add express port 3101 j to the first degree 3101 b. The optical coupler 3130 a is used to broadcast wavelengths from the first degree 3101 a to the degree express port 31011 and the 2 by 1 WSS 3161 a. The 2 by 1 WSS 3161 a is used to pass and block wavelengths from the first degree and the degree express port 3101 k to optical coupler 3130 c. The optical coupler 3130 c is used to broadcast wavelengths that are to be dropped to both the drop expansion port 3101 h and the 1 by 2 WSS 3162 a. The 1 by 2 WSS 3162 a is used to select individual wavelengths to drop for the two embedded drop ports 3101 fg. The optical receivers of two transponders may be attached to the embedded drop ports 3101 fg. The drop expansion port 3101 h may be attached to an optical multiplexer/de-multiplexer circuit pack such as 2020 in FIG. 30.

On ROADM 3110 b, optical coupler 3131 d is used to combine individual wavelengths applied to the embedded add ports 3102 cd. The transmitter outputs of two transponders may be attached to embedded add ports 3102 cd. The add expansion port 3102 e may be attached to an optical multiplexer/de-multiplexer circuit pack such as 2020 in FIG. 30. Optical coupler 3131 c is used to combine the optical wavelengths from optical coupler 3131 d with the optical wavelengths received at the add expansion port 3102 e, and the combined wavelengths are broadcasted to both 3 by 1 WSS 3160 b and the add express port 3102 i. The optical coupler 3130 f is used to broadcast wavelengths received from the degree express port 3102 k to both the 3 by 1 WSS 3160 b and the 2 by 1 WSS 3161 b. The add express port 3102 j forwards added wavelengths from ROADM 3110 a to the 3 by 1 WSS 3160 b. The 3 by 1 WSS 3160 b is used to pass and block wavelengths from the embedded add ports 3102 cd, the add expansion port 3102 e, the degree express port 3102 k, and the add express port 3102 j to the second degree 3102 b. The optical coupler 3130 e is used to broadcast wavelengths from the second degree 3102 a to the degree express port 31021 and the 2 by 1 WSS 3161 b. The 2 by 1 WSS 3161 b is used to pass and block wavelengths from the second degree and the degree express port 3102 k to optical coupler 3130 g. The optical coupler 3130 g is used to broadcast wavelengths that are to be dropped to both the drop expansion port 3102 h and the 1 by 2 WSS 3162 b. The 1 by 2 WSS 3162 b is used to select individual wavelengths to drop for the two embedded drop ports 3102 fg. The optical receivers of two transponders may be attached to the embedded drop ports 3102 fg. The drop expansion port 3102 h may be attached to an optical multiplexer/de-multiplexer circuit pack such as 2020 in FIG. 30.

The connected degree express ports 31011 and 3102 k are used to forward all wavelengths received at the first degree 3101 a of the first ROADM 3110 a to the second ROADM 3110 b. At the second ROADM 3110 b, the wavelengths received from the first degree of the first ROADM may be either passed or blocked to the second degree 3102 b using 3160 a. Additionally, at the second ROADM 3110 b, the wavelengths received from the first degree of the first ROADM may be dropped to the embedded drop ports 3102 fg of the second ROADM and the drop expansion port 3102 h.

The connected degree express ports 3101 k and 31021 are used to forward all wavelengths received at the second degree 3102 a of the second ROADM 3110 b to the first ROADM 3110 a. At the first ROADM 3110 a, the wavelengths received from the second degree of the second ROADM may be either passed or blocked to the first degree 3101 b using 3160 a. Additionally, at the first ROADM 3110 a, the wavelengths received from the second degree of the second ROADM may be dropped to the embedded drop ports 3101 fg of the first ROADM and the drop expansion port 3101 h.

Since wavelengths from either the first degree 3101 a or from the second degree 3102 a can be dropped to any of the embedded drop ports 3101 fg,3102 fg on either ROADM, the embedded drop ports 3101 fg,3102 fg are directionless. Also, since wavelengths from either the first degree 3101 a or from the second degree 3102 a can be dropped to both drop expansion ports 3101 h,3102 h on either ROADM, the drop expansion ports 3101 h,3102 h are directionless.

The connected add express ports 3101 i and 3102 j are used to forward added wavelengths received at embedded add ports 3101 cd and add expansion port 3101 e of the first ROADM 3110 a to the second ROADM 3110 b. At the second ROADM 3110 b, the received add wavelengths from the first ROADM can be either passed or blocked to the second degree 3102 b using 3160 b. Similarly, the connected add express ports 3101 j and 3102 i are used to forward added wavelengths received at embedded add ports 3102 cd and add expansion port 3102 e of the second ROADM 3110 b to the first ROADM 3110 a. At the first ROADM 3110 a, the received add wavelengths from the second ROADM can be either passed or blocked to the first degree 3101 b using 3160 a. Since wavelengths added at the add ports 3101 c-e of the first ROADM 3110 a and wavelengths added at the add ports 3102 c-e of the of the second ROADM 3110 b can be forwarded out the first degree 3101 b and the second degree 3102 b via the add express ports, the add ports 3101 c-e and 3102 c-e are directionless add ports.

FIG. 32 illustrates an optical node 3200 that is identical to optical node 3100, except that the WSS devices in each ROADM are replaced by wavelength equalizers and optical couplers. Namely, the 3 by 1 WSS 3160 a is implemented using wavelength equalizers 3251 c-e and optical couplers 3231 bc, and the 2 by 1 WSS 3161 a is replaced by wavelength equalizers 3251 ab and optical coupler 3231 a, and the 1 by 2 WSS 3162 a is replaced by wavelength equalizers 3251 fg and optical coupler 3230 a. Similarly, the 3 by 1 WSS 3160 b is implemented using wavelength equalizers 3251 j-1 and optical couplers 3231 ef, and the 2 by 1 WSS 3161 b is replaced by wavelength equalizers 3251 hi and optical coupler 3231 d, and the 1 by 2 WSS 3162 b is replaced by wavelength equalizers 3251 mn and optical coupler 3230 b.

The wavelength equalizers 3251 a-g may be contained within a wavelength equalizing array 3250 a. Similarly, the wavelength equalizers 3251 h-n may be contained within a wavelength equalizing array 3250 b.

On the first ROADM 3210 a, it can be stated that wavelength equalizer 3251 a is used to pass and block wavelengths from the first optical degree 3101 a to the embedded drop ports 3101 fg and the drop expansion port 3101 h, and the wavelength equalizer 3251 b is used to pass and block wavelengths from the second optical degree 3102 a to the embedded drop ports 3101 fg and the drop expansion port 3101 h, and the wavelength equalizer 3251 c is used to pass and block wavelengths from the second optical degree 3102 a to the first optical degree 3101 b, and the wavelength equalizer 3251 d is used to pass and block wavelengths from embedded add ports 3101 cd and add expansion port 3101 e on the first ROADM 3210 a to the first optical degree 3101 b, and the wavelength equalizer 3251 e is used to pass and block wavelengths from the embedded add ports 3102 cd and add expansion port 3102 h on the second ROADM 3210 b to the first optical degree 3101 b, and the wavelength equalizer 3251 f is used to pass and block wavelengths from the first optical degree 3101 a and the second optical degree 3102 a to the first embedded drop port 3101 g on the first ROADM 3210 a, and the wavelength equalizer 3251 g is used to pass and block wavelengths from the first optical degree 3101 a and the second optical degree 3102 a to the second embedded drop port 3101 f on the first ROADM 3210 a.

Similarly, on the second ROADM 3210 b, it can be stated that wavelength equalizer 3251 h is used to pass and block wavelengths from the second optical degree 3102 a to the embedded drop ports 3102 fg and the drop expansion port 3102 h, and the wavelength equalizer 3251 i is used to pass and block wavelengths from the first optical degree 3101 a to the embedded drop ports 3102 fg and the drop expansion port 3102 h, and the wavelength equalizer 3251 j is used to pass and block wavelengths from the first optical degree 3101 a to the second optical degree 3102 b, and the wavelength equalizer 3251 k is used to pass and block wavelengths from embedded add ports 3102 cd and add expansion port 3102 e on the second ROADM 3210 b to the second optical degree 3102 b, and the wavelength equalizer 32511 is used to pass and block wavelengths from the embedded add ports 3101 cd and add expansion port 3101 h on the first ROADM 3210 a to the second optical degree 3102 b, and the wavelength equalizer 3251 m is used to pass and block wavelengths from the second optical degree 3102 a and the first optical degree 3101 a to the first embedded drop port 3102 g on the second ROADM 3210 b, and the wavelength equalizer 3251 n is used to pass and block wavelengths from the first optical degree 3101 a and the second optical degree 3102 a to the second embedded drop port 3102 f on the second ROADM 3210 b.

FIG. 33A is an illustration of a wavelength equalizing array 3700 containing eight wavelength equalizers that can be configured to be any combination of 1 by 1 wavelength selective switches or 2 by 1 wavelength selective switches or 1 by 2 wavelength selective switches. Each wavelength directing function 3725 a-d behaves in a manner identical to the wavelength directing functions 511 a-c of wavelength equalizing array 510 if the inputs and outputs of each wavelength equalizer 3725 a-d have their numbering reversed. The wavelength equalizing array 3700 may also be considered to be a wavelength switch, as it is operable to switch individual wavelengths of a WDM optical signal having r individual wavelengths.

FIG. 33B is a simplified schematic diagram of the wavelength equalizing array (wavelength switch) 3700 of FIG. 33A, that shows the permissible flow of wavelengths through the wavelength equalizing array. For instance, the top horizontal arrow within 3725 a of FIG. 33B illustrates that wavelengths may be directed from the first input to the first output, and the bottom horizontal arrow within 3725 a of FIG. 33B illustrates that wavelengths may be directed from the second input to the second output, and the diagonal arrow within 3725 a of FIG. 33B indicates that wavelengths may be directed from the second input to the first output, while the lack of a diagonal arrow between the first input and the second output illustrates that wavelengths cannot be directed from the first input to the second output.

FIG. 33C is a simplified schematic diagram of a wavelength equalizing array like that of FIG. 33A, except it only contains six wavelength equalizers.

FIG. 34 is an illustration of a ROADM 3800 comprising of one optical degree 3101 ab, one degree express port 3101 k 1, one add express port 3101 ij, embedded add/drop ports 3101 cd,3101 fg, and an add/drop expansion port 3101 e,3101 h. The ROADM 3800 behaves identically to the ROADM 3110 a of FIG. 31, with the exception that the ROADM 3800 includes a photodiode 1994 used for wavelength power level measuring, a tunable filter 3812 used to select a wavelength for the photodiode 1994, optical taps in the form of 1 to 2 optical couplers 3130 ef used to broadcast the wavelengths arriving and exiting the optical degree to a broadband 2 to 1 optical switch 3833 (waveguide 2 to 1 optical switch), wherein the optical switch 3833 is used to forward either wavelengths arriving at 3101 a or wavelengths exiting 3101 b to the tunable filter 3812.

FIG. 35 shows the ROADM of FIG. 34 constructed using the wavelength equalizing array (wavelength switch) 3700 of FIG. 33A. As can be seen in FIG. 35, the ROADM 3900 no longer includes the 3 by 1 WSS 3160 a, the 2 by 1 WSS 3161 a, the 1 by 2 WSS 3162 a, or the tunable filter 3812 shown in the ROADM 3800. Instead, within the ROADM 3900, the optical device 3700 along with the coupler 3931 is used to replace all of these functions. In the ROADM 3900, the top portion of wavelength directing function 3725 a is used to replace the tunable filter 3812, the bottom portion of wavelength directing function 3725 a is combined with the wavelength directing function 3725 b to replace the 3 by 1 WSS 3160 a (using the coupler 3931), the wavelength directing function 3725 c is used to replace the 2 by 1 WSS 3161 a, and the wavelength directing function 3725 d is used to replace the 1 by 2 WSS 3162 a. This example illustrates the extreme versatility of the wavelength directing functions within 3700.

FIG. 36 is an illustration of a two-degree optical node 4000 comprised of two ROADMs 4010 ab with embedded directionless add/drop ports 3101 cdm,3101 fgn and 3102 cdm,3102 fgn. Each of the ROADMs 4010 ab behaves identically to the ROADM 3110 a of FIG. 31, except that the ROADMs 4010 ab each contain one additional embedded add/drop port (3 ports instead of 2). Because of this, each of the ROADMs 4010 ab contains a 1 by 3 WSS instead of a 1 by 2 WSS.

FIG. 37 is an illustration of a two-degree optical node 4100 comprised of two ROADMs 4110 ab with embedded add/drop ports 3101 cdmopq,3101 fgnrst and 3102 cdmopq,3102 fgnrst that are not directionless. The ROADMs 4110 ab are similar to the ROADMs 4010 ab of FIG. 36, except the ROADMS 4010 ab each have three embedded “directionless” add/drop ports, while the ROADMs 4110 ab each have six embedded add drop ports that are “not directionless” (but instead dedicated to a degree). Because of these differences, the ROADMs 4110 ab each contain one 2 by 1 WSS and one 1 by 6 WSS (instead of the one 3 by 1 WSS, the one 2 by 1 WSS, and the one 1 by 3 WSS contained on the ROADMs 4010 ab).

FIG. 38A is an illustration of a ROADM 4200 with two operating modes, constructed using the wavelength equalizing array (wavelength switch) 3700 of FIG. 33A. The ROADM 4200 can be configured to operate in a first mode such that it performs the function of the ROADM 4010 a of FIG. 36, and the ROADM 4200 can be configured to operate in a second mode such that it performs the function of the ROADM 4110 a of FIG. 37. It does this by replacing all the WSS devices contained within ROADMs 4010 a and 4110 a with the optical device 3700 of FIG. 33A. Configuring the ROADM 4200 to perform the function of ROADM 4010 a or ROADM 4110 a is done by configuring the 2×2 broadband optical switch 4244, configuring the 1×2 broadband optical switch 4234, and by configuring the five switchable optical couplers 4231 ab, 4230 a-c.

The broadband optical switches 4244 and 4234 are designed to switch an entire band of wavelengths (such as the r wavelengths shown within optical device 3700 of FIG. 33A). The broadband switches 4244 and 4234 are waveguide switches, meaning they switch at the waveguide level (i.e., the fiber level). This means that broadband switch 4234 directs ALL the wavelengths arriving on its input waveguide (i.e., input fiber) to either its top waveguide output (directed to coupler 4231 b) or to its bottom waveguide output (directed to optical port 3101 r). The broadband switch 4234 is not capable of directing some wavelengths to its top output and some wavelengths to its bottom output, but instead it directs all wavelengths to the top output or all wavelengths to the bottom output. Therefore, the 1×2 broadband (waveguide) switch 4234 can be implemented much simpler than a 1 by 2 WSS device, which is considered to be a wavelength switch, rather than a waveguide switch, as the 1 by 2 WSS device can selectively switch different wavelengths to each of its two output ports. For example, the 1×2 broadband switch (i.e., waveguide switch) may be implemented with simple Mach-Zehnder Interferometers.

The switchable optical couplers 4231 ab and 4230 a-c in ROADM 4200 are able to be configured with two different optical coupling ratios, the first optical coupling ratio may be that of a simple 50/50 ratio, while the second optical coupling ratio may be a 99/1 coupling ratio, although the switchable coupler (SC) is not limited to these two ratios.

As shown in FIG. 38B, in order to configure the ROADM 4200 to perform the function of ROADM 4010 a of FIG. 36, switchable coupler 4231 a is set to a 99/1 coupling ratio with 99% of the light at the output of the coupler 4231 a from the coupler 3332 a (essential creating a direct connect from coupler 3332 a to coupler 3131 a). In addition, switchable coupler 4230 c is set to a 50/50 coupling ratio, thus mimicking the 1 to 2 coupler 3130 d of ROADM 4010 a. In addition, switchable coupler 4230 a is set to a 99/1 coupler, thereby creating essentially a direct connection from coupler 3130 a to 3725 c. In addition, coupler 4231 b is set to a 50/50 coupling ratio. In addition, switchable coupler 4230 b is set to be a 50/50 coupler. In addition, 1×2 switch 4234 is set to connect its input to coupler 4231 b. In addition, 2×2 switch 4244 is set to the cross state, thereby connecting the output of 3725 c to coupler 4234 a. The 3 by 1 WSS 4270 is formed by the combination of 3725 a, the upper half of 3725 b, and coupler 4231 b. The 2 by 1 WSS 4271 is formed by 3725 c. The 1 by 3 WSS 4272 ab is formed by 3725 d and the lower half of 3725 b and coupler 4234 b.

As shown in FIG. 38C, in order to configure the ROADM 4200 to perform the function of ROADM 4110 a of FIG. 37, switchable coupler 4230 b is set to a 99/1 coupling ratio, essentially creating a direct connect from input 3101 k to 3725 a. In addition, switchable coupler 4231 a is set to a 50/50 coupling ratio. In addition, switchable coupler 4230 c is set to a 99/1 coupler, thereby creating essentially a direct connection from coupler 3131 a to 3725 a. In addition, coupler 4230 a is set to a 50/50 coupling ratio. In addition, switchable coupler 4231 b is set to a 99/1 coupler, essentially creating a direct connection from 3725 a to amplifier 3141 a. In addition, 1×2 switch 4234 is set to connect its input to output 3101 r. In addition, 2×2 switch 4244 is set to the straight through state, thereby connecting the output of 3725 c to output 3101 t, and also connecting the lower output of coupler 4230 a to coupler 4234 a. The 2 by 1 WSS 4281 is formed by 3725 a. The 1 by 6 WSS 4282 is formed by 3725 b-d and couplers 4230 a, 4234 a, and 4234 b, as shown in greater detail in FIG. 38D.

ROADM 4200 illustrates how in a first mode of operation, a wavelength directing function 3725 c can be utilized as a 2 by 1 WSS device, while in a second mode of operation the same wavelength directing function 3725 c can be utilized as a 1 by 2 WSS device. It also illustrates how in the first mode of operation the unused output of the wavelength directing function 3725 c (the output connected to port 3101 s) can be connected in anticipation of using the output for the second mode of operation. Also, it shows a given input of the wavelength directing function (the input connected to coupler 4230 b) can be connected to the wavelength directing function for use only during the first mode of operation. Therefore, when converting a wavelength directing function 3725 c between a 2 by 1 WSS and a 1 by 2 WSS, one input of the wavelength directing function is always dedicated to the 2 by 1 WSS function, and one output is always dedicated to the 1 by 2 WSS function, and at most only one input and one output of the wavelength directing function need to be connected to other signals when going between the two modes.

It should be noted that the individual wavelength switches used within the various wavelength equalizing arrays (such as switches 513 a, 514 a, and 3326 a shown in 3600 of FIG. 36), may be implemented with ring resonators within a photonic integrated chip (PIC). Alternatively, free space optics may be used to create the individual wavelength switches.

FIG. 39A is an illustration of a wavelength switch 3910 containing two wavelength equalizers 100 a-b that can be configured to be two 1 by 1 wavelength selective switches (as shown in FIG. 39B) or one 1 by 2 wavelength selective switch (as shown in FIG. 39C) or one 2 by 1 wavelength selective switch (as shown in FIG. 39D). The wavelength switch 3910 comprises of a first optical input 3722 b; a second optical input 3722 a; a first optical output 3724 b; a second optical output 3724 a; a first optical coupler 4230 having a coupler input, a first coupler output, and a second coupler output, wherein the coupler input is connected to the first optical input 3722 b; a first waveguide switch 3833 having a first switch input, a second switch input, and a switch output, wherein the first switch input is connected to the second optical input 3722 a, and wherein the second switch input is connected to the first coupler output; a first wavelength equalizer 100 b having a first equalizer input and a first equalizer output, wherein the first equalizer input is connected to the second coupler output; a second wavelength equalizer 100 a having a second equalizer input and a second equalizer output, wherein the second equalizer input is connected to the switch output; a second waveguide switch 4234 having a switch input, a first switch output, and a second switch output, wherein the first equalizer output is connected to the switch input, and wherein the first switch output is connected to the first optical output 3724 b; and a second optical coupler 4231 having a first coupler input, a second coupler input, and a coupler output, wherein the first coupler input is connected to the second equalizer output, and wherein the second coupler input is connected to the second switch output, and wherein the coupler output is connected to the second optical output 3724 a.

Within the wavelength switch 3910, the first waveguide switch 3833 and the second waveguide switch 4234 are operable to be set to a first switch configuration (as shown in FIG. 39B), a second switch configuration (as shown in FIG. 39BC), and a third switch configuration (as shown in FIG. 39D), wherein when set to the first switch configuration (as shown in FIG. 39B), the first waveguide switch 3833 is set (switch in the up position) so as to forward a signal from the second optical input 3722 a to the second wavelength equalizer 100 a, and the second waveguide switch 4234 is set (switch in the down position) so as to forward a signal from the first wavelength equalizer 100 b to the first optical output 3724 b, and wherein when set to the second switch configuration (as shown in FIG. 39C), the first waveguide switch 3833 is set (switch in the down position) so as to forward a signal from the first optical coupler 4230 to the second wavelength equalizer 100 a, and the second waveguide switch 4234 is set (switch in the down position) so as to forward the signal from the first wavelength equalizer 100 b to the first optical output 3724 b, and wherein when set to the third switch configuration (as shown in FIG. 39D), the first waveguide switch 3833 is set (switch in the up position) so as to forward the signal from the second optical input 3722 a to the second wavelength equalizer 100 a, and the second waveguide switch 4234 is set (switch in the up position) so as to forward the signal from the first wavelength equalizer 100 b to the second optical output 3724 a.

When the two waveguide switches 3833, 4234 are set to the first switch configuration (as shown in FIG. 39B), the wavelength switch 3910 operates as two 1 by 1 wavelength selective switches. The first 1 by 1 wavelength selective switch is formed by the first optical input 3722 b, first optical coupler 4230, the first wavelength equalizer 100 b, the second waveguide switch 4234, and the first optical output 3724 b, while the second 1 by 1 wavelength selective switch is formed by the second optical input 3722 a, the first waveguide switch 3833, the second wavelength equalizer 100 a, second optical coupler 4231 and the second optical output 3724 a. For the first switch configuration, the first optical coupler 4230 operates in manner similar to that of an optical switch—effectively connecting the coupler input to the second coupler output (as shown in FIG. 39B). Similarly, for the first switch configuration, the second optical coupler 4231 operates in manner similar to that of an optical switch—effectively connecting the first coupler input to the coupler output (as shown in FIG. 39B).

When the two waveguide switches 3833, 4234 are set to the second switch configuration (as shown in FIG. 39C), the wavelength switch 3910 operates as one 1 by 2 wavelength selective switch, wherein the first optical input 3722 b is the input to the WSS, and the first optical output 3724 b and the second optical output 3724 a are the two outputs of the WSS. For the second switch configuration, the first optical coupler 4230 acts as a 1:2 optical coupler, and is used to broadcast incoming wavelengths to both the first wavelength equalizer 100 b and the second wavelength equalizer 100 a, while the second optical coupler 4231 operates in manner similar to that of an optical switch effectively connecting the first coupler input to the coupler output (as shown in FIG. 39C).

When the two waveguide switches 3833, 4234 are set to the third switch configuration (as shown in FIG. 39D), the wavelength switch 3910 operates as one 2 by 1 wavelength selective switch, wherein the first optical input 3722 b and the second optical input 3722 a are the two inputs to the WSS, and the second optical output 3724 a is the output of the WSS. For the third switch configuration, the second optical coupler 4231 acts as a 2:1 optical coupler, and is used to combine wavelengths exiting the first wavelength equalizer 100 b with wavelengths from the second wavelength equalizer 100 a, while the first optical coupler 4230 operates in manner similar to that of an optical switch—effectively connecting the coupler input to the second coupler output (as shown in FIG. 39D).

The wavelength switch 3910 is operable to be programmed to a first mode of operation (as shown in FIG. 39B), a second mode of operation (as shown in FIG. 39C), and a third mode of operation (as shown in FIG. 39D), wherein when programmed to the first mode of operation (as shown in FIG. 39B), the wavelength switch 3910 passes and blocks individual wavelengths between the first optical input 3722 b and the first optical output 3724 b, and the wavelength switch 3910 passes and blocks individual wavelengths between the second optical input 3722 a and the second optical output 3724 a, and wherein when programmed to the second mode of operation (as shown in FIG. 39C), the wavelength switch 3910 passes and blocks individual wavelengths between the first optical input 3722 b and the first optical output 3724 b, and the wavelength switch 3910 passes and blocks individual wavelengths between the first optical input 3722 b and the second optical output 3724 a, and wherein when programmed to the third mode of operation (as shown in FIG. 39D), the wavelength switch 3910 passes and blocks individual wavelengths between the first optical input 3722 b and the second optical output 3724 a, and the wavelength switch 3910 passes and blocks individual wavelengths between the second optical input 3722 a and the second optical output 3724 a.

Within the wavelength switch 3910, the first optical coupler 4230 may be a first switchable optical coupler operable to be programmed to a first optical coupler first coupling ratio and to a first optical coupler second coupling ratio, and the second optical coupler 4231 may be a second switchable optical coupler operable to be programmed to a second optical coupler first coupling ratio and to a second optical coupler second coupling ratio.

The first optical coupler first coupling ratio may be such that greater than 90% of the light from the coupler input is directed to the first wavelength equalizer 100 b (as shown in FIG. 39B), and less than 10% of the of the light from the coupler input is directed to the first waveguide switch. In such a configuration, the coupler 4230 acts essentially like an optical switch whose coupler input is connected to the second coupler output, and therefore it is depicted that way, as indicate in FIG. 39B, which shows a solid line between the coupler input of coupler 4230 and the second coupler output, and is shown with no line connecting the coupler input of coupler 4230 to the first coupler output.

The first optical coupler second coupling ratio may be such that the light from the coupler input is more evenly distributed to the first wavelength equalizer 100 b and the first waveguide switch 3833 (as shown in FIG. 39C). In such a configuration, the coupler 4230 acts more like 2:1 coupler than an optical switch, and therefore it is depicted that way, as indicated in FIG. 39C. The first optical coupler second coupling ratio may be a 50/50 coupling ratio, or it may be a coupling ratio such a higher percentage of the light inputted to the coupler is forwarded to the first waveguide switch 3833, since the light path through the second wavelength equalizer 100 a has slightly more insertion loss than the light path through the first wavelength equalizer 100 b.

Similarly, the second optical coupler first coupling ratio may be such that greater than 90% of the light exiting the second optical coupler 4231 is from the second wavelength equalizer 100 a, and less than 10% of the of the light exiting the second optical coupler 4231 is from the second waveguide switch waveguide switch 4234 (as shown in FIG. 39B). In such a configuration, the coupler 4231 acts essentially like an optical switch whose first coupler input is connected to the coupler output, and therefore it is depicted that way, as indicated in FIG. 39B, which shows a solid line between the first coupler input of coupler 4231 and the coupler output, and is shown with no line connecting the second coupler input of coupler 4231 to the coupler output.

Similarly, the second optical coupler second coupling ratio may be such that a more even amount of light from the first coupler input and the second coupler input is directed to the coupler output of coupler 4231 (as depicted in FIG. 39D). Therefore, in FIG. 39D, the coupler 4231 is depicted as a 2:1 coupler, and not as an optical switch.

Within the wavelength switch 3910, the first optical coupler 4230 may be a first variable optical coupler operable to be programmed to a first optical coupler first coupling ratio and to a first optical coupler second coupling ratio, and the second optical coupler 4231 may be a second variable optical coupler operable to be programmed to a second optical coupler first coupling ratio and to a second optical coupler second coupling ratio.

Within the wavelength switch 3910, the first waveguide switch 3833 and the second waveguide switch 4234 are operable to be set to a first switch configuration (See FIG. 39B), a second switch configuration (See FIG. 39C), and a third switch configuration (See FIG. 39D), wherein when set to the first switch configuration (FIG. 39B), the first wavelength equalizer 100 b passes and blocks individual wavelengths between the first optical input 3722 b and the first optical output 3724 b, and the second wavelength equalizer 100 a passes and blocks individual wavelengths between the second optical input 3722 a and the second optical output 3724 a, and wherein when set to the second switch configuration (FIG. 39C), the first wavelength equalizer 100 b passes and blocks individual wavelengths between the first optical input 3722 b and the first optical output 3724 b, and the second wavelength equalizer 100 a passes and blocks individual wavelengths between the first optical input 3722 b and the second optical output 3724 a, and wherein when set to the third switch configuration (FIG. 39D), the first wavelength equalizer 100 b passes and blocks individual wavelengths between the first optical input 3722 b and the second optical output 3724 a, and the second wavelength equalizer 100 a passes and blocks individual wavelengths between the second optical input 3722 a and the second optical output 3724 a. Furthermore, the first optical coupler 4230 may be a first switchable optical coupler operable to be programmed to a first optical coupler first coupling ratio and to a first optical coupler second coupling ratio, and the second optical coupler 4231 may be a second switchable optical coupler operable to be programmed to a second optical coupler first coupling ratio and to a second optical coupler second coupling ratio, wherein when set to the first switch configuration (as shown in FIG. 39B), the first optical coupler is set to direct its inputted light to the first wavelength equalizer 100 b and to direct none of its inputted light to the first waveguide switch 3833, and the second optical coupler 4231 is set to direct light from the second wavelength equalizer 100 a to the second optical output 3724 a and to direct no light from the second waveguide switch 4234 to the second optical output 3724 a, and wherein when set to the second switch configuration (as shown in FIG. 39C), the first optical coupler 4230 is set to direct a first portion of is inputted light to the first wavelength equalizer 100 b, and to direct a second portion of is inputted light to the first waveguide switch 3833, and the second optical coupler 4231 is set to direct light from the second wavelength equalizer 100 a to the second optical output 3724 a and to direct no light from the second waveguide switch 4234 to the second optical output 3724 a, and wherein when set to the third switch configuration (as shown in FIG. 39D), the first optical coupler 4230 is set to direct its inputted light to the first wavelength equalizer 100 b and to direct none of its inputted light to the first waveguide switch 3833, and the second optical coupler 4231 is set to combine light from the first wavelength equalizer 100 b with light from the second wavelength equalizer 100 a.

Furthermore, within the wavelength switch 3910, the first wavelength equalizer 100 b may have only one optical input and only one optical output, as depicted in FIG. 39A, and the second wavelength equalizer 100 a may have only one optical input and only one optical output, as depicted in FIG. 39A.

As shown in FIG. 40A, four of the wavelength switches 3910 a-d may be combined to form one larger wavelength switch 4300. The wavelength switch 4300 may also be considered to be a wavelength equalizing array that is functionally equivalent to the wavelength equalizing array (wavelength switch) 3700 depicted in FIG. 33A and FIG. 33B. Therefore, the wavelength switch 4300 may be substituted for the wavelength switch 3700 within ROADMs 3900, 4200, 4210 a, and 4210 b without any loss of functionality. Furthermore, wavelength switch 4300 (of FIG. 40) has additional functionality that wavelength switch 3700 does not include when using wavelength switch 4300 to implement 1 by 2 wavelength selective switches. More specifically, when programming a wavelength switch 3910 a-d within wavelength switch 4300 to be a 1 by 2 WSS, wavelengths entering the 1 by 2 WSS may be broadcasted to both outputs of the WSS. This functionality is enabled by the first optical coupler 4230 within a given 1 by 2 WSS element of 3910 when programmed as depicted in FIG. 39C.

The optical switch 4300 comprises optical switches 3910 a-d, optical inputs 3722 a-h connected to the optical inputs of optical switches 3910 a-d, and optical outputs 3724 a-h, connected to the optical outputs of optical switches 3910 a-d. Optical switch 3910 a comprises switchable optical couplers 4230 a and 4231 a, and waveguide switches 3833 a and 4234 a, and wavelength equalizers 100 a-b. Similarly, optical switch 3910 b comprises switchable optical couplers 4230 b and 4231 b, and waveguide switches 3833 b and 4234 b, and wavelength equalizers 100 c-d. Similarly, optical switch 3910 c comprises switchable optical couplers 4230 c and 4231 c, and waveguide switches 3833 c and 4234 c, and wavelength equalizers 100 e-f. Similarly, optical switch 3910 d comprises switchable optical couplers 4230 d and 4231 d, and waveguide switches 3833 d and 4234 d, and wavelength equalizers 100 g-h.

FIG. 40B is a simplified schematic diagram of the wavelength equalizing array (wavelength switch) 4300 of FIG. 40A, that shows the permissible flow of wavelengths through the wavelength equalizing array. For instance, the top horizontal arrow within 3910 a of FIG. 40B illustrates that wavelengths may be directed from the first input 3722 a to the first output 3724 a, and the bottom horizontal arrow within 3910 a of FIG. 40B illustrates that wavelengths may be directed from the second input 3722 b to the second output 3724 b, and the diagonal arrow within 3910 a of FIG. 40B indicates that wavelengths may be directed from the second input 3722 b to the first output 3724 a, while the lack of a diagonal arrow between the first input 3722 a and the second output 3724 b illustrates that wavelengths cannot be directed from the first input 3722 a to the second output 3724 b.

FIG. 41 is a two-degree node 4400 that uses two instances of the ROADM 4200 of FIG. 38A configured to mimic the optical node 4000 of FIG. 36. In FIG. 41, the first ROADM 4200 a is optically connected to the second ROADM 4200 b using four optical jumper cables 3190 a-d.

FIG. 42 is a two-degree node 4500 that uses two instances of the ROADM 4200 of FIG. 38A configured to mimic the optical node 4100 of FIG. 37. In FIG. 42, the first ROADM 4200 a is optically connected to the second ROADM 4200 b using two optical jumper cables 3190 a-b.

FIG. 43 is a two-degree node 4600 that uses two instances of the ROADM 4550 configured to mimic the optical node 4000 of FIG. 36. The ROADM 4550 is identical to the ROADM 4200, except that the optical switch 3700 is replaced with the optical switch 4300, without any loss of functionality. In FIG. 43, the first ROADM 4550 a is optically connected to the second ROADM 4550 b using four optical jumper cables 3190 a-d.

FIG. 44 is a two-degree node 4700 that uses two instances of the ROADM 4550 configured to mimic the optical node 4100 of FIG. 37. The ROADM 4550 is identical to the ROADM 4200, except that the optical switch 3700 is replaced with the optical switch 4300, without any loss of functionality. In FIG. 44, the first ROADM 4550 a is optically connected to the second ROADM 4550 b using two optical jumper cables 3190 a-b.

The optical node 4400/4500 (FIG. 41-42) comprises of a first optical degree (with degree input 3101 a of 4200 a, and degree output 3101 b of 4200 a), a second optical degree (with degree input 3101 a of 4200 b, and degree output 3101 b of 4200 b), a first plurality of drop ports (3101 f, 3101 g, 3101 n of 4200 a), a second plurality of drop ports (3101 f, 3101 g, 3101 n of 4200 b), a first wavelength switch (3700 of 4200 a), used to select individual wavelengths for the first optical degree (output 3101 b of 4200 a) and used to select individual wavelengths for the first plurality of drop ports (3101 f, 3101 g, 3101 n of 4200 a), a second wavelength switch (3700 of 4200 b), used to select individual wavelengths for the second optical degree (output 3101 b of 4200 b), and used to select individual wavelengths for the second plurality of drop ports (3101 f, 3101 g, 3101 n of 4200 b), and a plurality of waveguide switches (4244 and 4234 of 4200 a, and 4244 and 4234 of 4200 b), operable to be set to a first mode (as shown in node 4400) and to a second mode (as shown in 4500), wherein when the plurality of waveguide switches are set to the first mode (as shown in 4400), the first plurality of drop ports (3101 f, 3101 g, 3101 n of 4200 a) are operable to drop wavelengths from the first optical degree (3101 a of 4200 a) and from the second optical degree (3101 a of 4200 b), and the second plurality of drop ports (3101 f, 3101 g, 3101 n of 4200 b) are operable to drop wavelengths from the first optical degree (3101 a of 4200 a) and from the second optical degree (3101 a of 4200 b), and wherein when the plurality of waveguide switches are set to the second mode (as shown in 4500), the first plurality of drop ports (3101 f, 3101 g, 3101 n of 4200 a) are operable to drop wavelengths only from the first optical degree (3101 a of 4200 a), and the second plurality of drop ports (3101 f, 3101 g, 3101 n of 4200 b) are operable to drop wavelengths only from the second optical degree (3101 a of 4200 b).

In the first mode (4400), wavelengths from the first optical degree (3101 a of 4200 a) are sent to the second wavelength switch (3700 of 4200 b) via optical jumper cable 3190 a, wherein within ROADM 4200 b switchable optical coupler 4230 b is used to forward the wavelengths from the first optical degree to optical switch 3725 c of 4200 b, where optical switch 3725 c of 4200 b is configured as a 2 by 1 WSS (as indicated), which is used to select wavelengths from the first optical degree (3101 a of 4200 a) and the second optical degree (3101 a of 4200 b). In a similar manner, wavelengths from the second optical degree are able to be selected for the first plurality of drop ports using switch 3725 c of 4200 a,

In the second mode (4500), wavelengths from the first optical degree (3101 a of 4200 a) are sent to the second ROADM 4200 b via optical jumper cable 3190 a (like in the first mode), but in the second mode, optical switch 3725 c of 4200 b is configured as a 1 by 2 WSS, and therefore any wavelengths that could possibly be arriving at the top input of 3725 c of 4200 b are prevented from being switched by optical switch 3725 c of 4200 b. Because of this, switchable coupler 4230 b of 4200 b is set so as to forward all of its inputted light to optical switch 3725 a of 4200 b, as indicated be the solid line through switchable coupler 4230 b. In a similar manner, wavelengths from the second optical degree are prevented from exiting switch 3725 c of 4200 a.

Similarly, the optical node 4600/4700 (FIG. 43-44) comprises of a first optical degree (with degree input 3101 a of 4550 a, and degree output 3101 b of 4550 a), a second optical degree (with degree input 3101 a of 4550 b, and degree output 3101 b of 4550 b), a first plurality of drop ports (3101 f, 3101 g, 3101 n of 4550 a), a second plurality of drop ports (3101 f, 3101 g, 3101 n of 4550 b), a first wavelength switch (4300 of 4550 a), used to select individual wavelengths for the first optical degree (output 3101 b of 4550 a) and used to select individual wavelengths for the first plurality of drop ports (3101 f, 3101 g, 3101 n of 4550 a), a second wavelength switch (4300 of 4550 b), used to select individual wavelengths for the second optical degree (output 3101 b of 4550 b), and used to select individual wavelengths for the second plurality of drop ports (3101 f, 3101 g, 3101 n of 4550 b), and a plurality of waveguide switches (4244 and 4234 of 4200 a, and 4244 and 4234 of 4550 b), operable to be set to a first mode (as shown in node 4600) and to a second mode (as shown in 4700), wherein when the plurality of waveguide switches are set to the first mode (as shown in 4600), the first plurality of drop ports (3101 f, 3101 g, 3101 n of 4550 a) are operable to drop wavelengths from the first optical degree (3101 a of 4550 a) and from the second optical degree (3101 a of 4550 b), and the second plurality of drop ports (3101 f, 3101 g, 3101 n of 4550 b) are operable to drop wavelengths from the first optical degree (3101 a of 4550 a) and from the second optical degree (3101 a of 4550 b), and wherein when the plurality of waveguide switches are set to the second mode (as shown in 4700), the first plurality of drop ports (3101 f, 3101 g, 3101 n of 4550 a) are operable to drop wavelengths only from the first optical degree (3101 a of 4550 a), and the second plurality of drop ports (3101 f, 3101 g, 3101 n of 4550 b) are operable to drop wavelengths only from the second optical degree (3101 a of 4550 b).

In the optical nodes 4400/4500 and 4600/4700, when the plurality of waveguide switches are set to the second mode, the WSS used to select wavelengths for the optical degree outputs are only required to be 2 by 1 WSSs (instead of 3 by 1 WSSs), and the 2 by 1 WSS used to select dropped wavelengths from both input degrees is not required. Therefore, the wavelength switching resources used for this reduced functionality can be redeployed in order to provide additional drop ports on each ROADM. This allows each ROADM in FIG. 42 and FIG. 44 to have more drop ports than in each of the ROADMS in FIG. 41 and FIG. 43. Therefore, when the plurality of waveguide switches are set to the first mode, there are n number of drop ports that are operable to drop wavelengths (where n=3), and wherein when the plurality of waveguide switches are set to the second mode there are m number of drop ports that are operable to drop wavelengths (where m=6). And therefore, as can be seen, m is greater than n.

Since the optical node 4600/4700 utilizes wavelength switch 4300 (FIG. 40A/B), the first wavelength switch (4300 in 4550 a) comprises a first plurality of wavelength equalizers 100 a-h, and the second wavelength switch (4300 in 4550 b) comprises a second plurality of wavelength equalizers 100 a-h. Furthermore, each wavelength equalizer 100 a-h in wavelength switch 4300 comprises only one optical input and only one optical output. In addition, the plurality of waveguide switches (4244, 4234) are operable to switch wavelength division multiplexed optical signals, but they and are not operable to switch individual wavelengths within wavelength division multiplexed optical signals. In addition, the plurality of waveguide switches includes a first waveguide switch 4234 having an optical input port, a first optical output port, and a second optical output port, wherein the first waveguide switch is operable to switch an inputted wavelength division multiplexed optical signal from the optical input port to the first optical output port, and wherein the first waveguide switch is operable to switch the inputted wavelength division multiplexed optical signal from the optical input port to the second optical output port, and wherein the first waveguide switch is not operable to simultaneously switch a first plurality of wavelengths of the inputted wavelength division multiplexed optical signal to the first optical output port and a second plurality of wavelengths of the inputted wavelength division multiplexed optical signal to the second optical output port.

FIG. 45 depicts a software programmable single-degree ROADM 5000. The ROADM 5000 can be software programmed (configured) to have between 1 and 4 express ports, and between k and k+3 add/drop ports. This is done by configuring the waveguide switches 3833 a-c, 4234 a-f, and variable couplers 5002 a-f, 5004 a-h. In addition to waveguide switches and variable couplers, the ROADM 5000 comprises optical input ports 5020 a-k, optical output ports 5021 a-k, wavelength equalizers 100 a-g, k:1 coupler 5006, 1:k coupler 5007, and optical amplifiers 5012 a-b. In addition, the wavelength equalizers 100 a-g may be contained within a single wavelength switch 5010. In addition, there is a repeatable group of optical elements 5015 a-c, which may be repeated any number of times in order to support additional express and add/drop ports.

FIG. 46A depicts a ROADM configuration 5051 wherein the ROADM 5000 is configured as a single-degree ROADM with one express port and k+3 add/drop ports. The equivalent functional diagram of the ROADM configuration 5051 is the ROADM 5061 shown in FIG. 46B. Two of the ROADMs 5051 or 5061 could be combined (by interconnecting their express ports) in order to form a two-degree optical node. The ROADM 5061 comprises express input port 5020 a, express output port 5021 a, degree input port 5020 k, degree output port 5021 k, drop expansion port 5021 j, add expansion port 5020 j, drop ports 5021 i, 5021 b, add ports 5020 i, 5020 c, 1:3 optical coupler 5009, 2:1 optical coupler 5004 h, WSS 5031, WSS 5045, optical coupler 5041, and optical amplifiers 5012 a-b.

In the ROADM 5051 of FIG. 46A, the 2×1 WSS 5045 of 5061 is comprised of wavelength equalizers 100 a-b and coupler 5004 g. In the ROADM 5051 of FIG. 46A, the 1×(k+3) WSS 5031 is comprised of wavelength equalizers 100 c-g and couplers 5002 a-c, 5002 f, and 5007. In the ROADM 5051 of FIG. 46A the waveguide switches 3833 a-c and 4234 a,c,e are configured to forward wavelengths from the degree in optical port to the wavelength equalizers 100 c-e, and the waveguide switches 4234 b,d,f are configured to forward wavelengths from the wavelength equalizers 100 c-e to the ports drop k+3, drop k+2, and drop k+1. In addition, the variable optical couplers 5004 b,d,f are configured as essentially waveguide switches in order to forward wavelengths from coupler 5004 g to the output optical amplifier 5012 b with as little optical insertion loss as possible.

FIG. 47A depicts a ROADM configuration 5052 wherein the ROADM 5000 is configured as a single-degree ROADM with two express ports and k+2 add/drop ports. The equivalent functional diagram of the ROADM configuration 5052 is the ROADM 5062 shown in FIG. 47B. Three of the ROADMs 5052 or 5062 could be combined (by interconnecting their express ports in a full mesh) in order to form a three-degree optical node. The ROADM 5062 comprises express input ports 5020 a-b, express output ports 5021 a,c, degree input port 5020 k, degree output port 5021 k, drop expansion port 5021 j, add expansion port 5020 j, drop ports 5021 i, 5021 b, add ports 5020 i, 5020 c, 1:3 optical coupler 5009, 2:1 optical coupler 5004 h, WSS 5032, WSS 5046, optical coupler 5042, optical coupler 5072, and optical amplifiers 5012 a-b. In the ROADM 5052 of FIG. 47A, the 3×1 WSS 5046 of 5062 is comprised of wavelength equalizers 100 a-c and couplers 5004 b,g. In the ROADM 5052 of FIG. 47A, the 1×(k+2) WSS 5032 is comprised of wavelength equalizers 100 d-g and couplers 5002 b-c, 5002 f, and 5007. In the ROADM 5052 of FIG. 47A the waveguide switches 3833 b-c and 4234 c,e are configured to forward wavelengths from the degree in optical port to the wavelength equalizers 100 d-e, and the waveguide switches 4234 d,f are configured to forward wavelengths from the wavelength equalizers 100 d-e to the ports drop k+2 and drop k+1, and the waveguide switch 3833 a is configured to forward the express in 2 signal to wavelength equalizer 100 c, and the waveguide switch 4234 a is configured to forward the degree in signal to the express 2 out port, and the waveguide switch 4234 b is configured to forward the signal from wavelength equalizer 100 c to the degree out port. In addition, the variable optical couplers 5004 d,f are configured as essentially waveguide switches in order to forward wavelengths from the wavelength equalizers 100 a-c to the output optical amplifier 5012 b with as little optical insertion loss as possible.

FIG. 48A depicts a ROADM configuration 5053 wherein the ROADM 5000 is configured as a single-degree ROADM with three express ports and k+1 add/drop ports. The equivalent functional diagram of the ROADM configuration 5053 is the ROADM 5063 shown in FIG. 48B. Four of the ROADMs 5053 or 5063 could be combined (by interconnecting their express ports in a full mesh) in order to form a four-degree optical node. The ROADM 5063 comprises express input ports 5020 a,d, express output ports 5021 a,e, degree input port 5020 k, degree output port 5021 k, drop expansion port 5021 j, add expansion port 5020 j, drop ports 5021 i, 5021 b, add ports 5020 i, 5020 c, 1:3 optical coupler 5009, 2:1 optical coupler 5004 h, WSS 5033, WSS 5047, optical coupler 5043, optical coupler 5073, and optical amplifiers 5012 a-b.

FIG. 49A depicts a ROADM configuration 5054 wherein the ROADM 5000 is configured as a single-degree ROADM with four express ports and k add/drop ports. The equivalent functional diagram of the ROADM configuration 5054 is the ROADM 5064 shown in FIG. 49B. Five of the ROADMs 5054 or 5064 could be combined (by interconnecting their express ports in a full mesh) in order to form a five-degree optical node. The ROADM 5064 comprises express input ports 5020 a,f, express output ports 5021 a,g, degree input port 5020 k, degree output port 5021 k, drop expansion port 5021 j, add expansion port 5020 j, drop ports 5021 i, 5021 b, add ports 5020 i, 5020 c, 1:3 optical coupler 5009, 2:1 optical coupler 5004 h, WSS 5034, WSS 5048, optical coupler 5043, optical coupler 5074, and optical amplifiers 5012 a-b.

Based upon the ROADM configurations 5051-5054, it can be seen that ROADM 5000 is operable to function as a ROADM in a first optical node, wherein the ROADM 5000 comprises: an optical degree output port 5021 k used to connect the first optical node to a second optical node; a plurality of optical express input ports 5020 a,b,d,f, used to connect the ROADM of the first optical node to additional ROADMs within the first optical node; one or more optical drop ports 5021 b,d,f,h,i; a wavelength switch 5010, used to switch individual wavelengths within wavelength division multiplexed optical signals; and a plurality of waveguide switches 3833 a-c, 4234 a-f that are programmable to perform a first function (such as that depicted in FIG. 46A) and a second function (such as that depicted in FIG. 47A), wherein when the plurality of waveguide switches are programmed to perform the first function (such as that depicted in FIG. 46A), the wavelength switch passes and blocks individual wavelengths to the optical degree output port from m number of the plurality of optical express input ports, and the wavelength switch 5010 passes and blocks individual wavelengths for n number of optical drop ports of the one or more optical drop ports, and wherein when the plurality of waveguide switches are programmed to perform the second function (such as that depicted in FIG. 47A), the wavelength switch 5010 passes and blocks individual wavelengths to the optical degree output port from m+j number of the plurality of optical express input ports, and the wavelength switch passes and blocks individual wavelengths for n−j number of optical drop ports of the one or more optical drop ports, wherein m, n, and j are integers greater than zero. Furthermore, since when the when the plurality of waveguide switches are programmed to perform the second function the number of optical drop ports of the one or more optical drop ports that the wavelength switch passes and blocks individual wavelengths for cannot be a negative number, j must be less than or equal to n (i.e., j≤n).

For example, if the waveguide switches 3833 a-c, 4234 a-f are programmed to perform a first function as shown in FIG. 46A, and then the waveguide switches 3833 a-c, 4234 a-f are then programmed to perform a second function as shown in FIG. 47A, then when the plurality of waveguide switches are programmed to perform the first function (FIG. 46A), the wavelength switch 5010 passes and blocks individual wavelengths to the optical degree output port 5021 k from m number of the plurality of optical express input ports (where m=1), and the wavelength switch 5010 passes and blocks individual wavelengths for n number of optical drop ports of the one or more optical drop ports (where n=k+3), and wherein when the plurality of waveguide switches are programmed to perform the second function (FIG. 47A), the wavelength switch passes and blocks individual wavelengths to the optical degree output port from m+j number of the plurality of optical express input ports (where m=1 and j=1, so that the number of express ports is equal to m+j=1+1=2), and the wavelength switch passes and blocks individual wavelengths for n−j number of optical drop ports of the one or more optical drop ports (wherein n=k+3, and j=1, and n−j=k+3−1=k+2, as depicted in FIG. 47A).

Similarly, if the waveguide switches 3833 a-c, 4234 a-f are programmed to perform a first function as shown in FIG. 46A, and then the waveguide switches 3833 a-c, 4234 a-f are then programmed to perform a second function as shown in FIG. 49A, then m=1, n=k+3, and j=3, so that when the plurality of waveguide switches are programmed to perform the second function (FIG. 49A), the wavelength switch passes and blocks individual wavelengths to the optical degree output port from m+j number of the plurality of optical express input ports (where m=1 and j=3, so that the number of express ports is equal to m+j=1+3=4), and the wavelength switch passes and blocks individual wavelengths for n−j number of optical drop ports of the one or more optical drop ports (wherein n=k+3, and j=3, and n−j=k+3−3=k, as depicted in FIG. 49A).

The wavelength switch 5010 within the ROADM 5000 may comprise of a plurality of wavelength equalizers 100 a-g, as shown in FIG. 45. And furthermore, each of the wavelength equalizers within the plurality of wavelength equalizers 100 a-g may comprise of only one optical input and only one optical output, as shown in FIG. 45. The ROADM 5000 may further comprise of a plurality of variable optical couplers 5004 b, 5004 d, 5004 f, 5004 g to combine optical outputs of the wavelength switch 5010, as shown in FIG. 45.

Furthermore, the plurality of waveguide switches within the ROADM 5000 may include an output waveguide switch (such as switch 4234 b), wherein when the plurality of waveguide switches are programmed to perform the first function (as depicted in FIG. 46A), the output waveguide switch 4234 b is used to forward one or more wavelengths from the wavelength switch 5010 to one optical drop port (5021 b) of the one or more optical drop ports, and wherein when the plurality of waveguide switches are programmed to perform the second function (as depicted in FIG. 47A), the output waveguide switch is used to forward one or more wavelengths from the wavelength switch 5010 to the optical degree output port 5012 b (via the path through 5004 b, 5004 d, 5004 f, and 5012 b).

The ROADM 5000 may further comprise an optical degree input port 5020 k used to connect the first optical node to the second optical node, and wherein the plurality of waveguide switches may include an input waveguide switch 3833 a, wherein when the plurality of waveguide switches are programmed to perform the first function, the input waveguide switch 3833 a is used to forward wavelengths from the optical degree input port 5020 k (via the path through 5012 a, 5002 e, 5002 f, 5002 d, 5002 a, 4234 a) to the wavelength switch 5010 (as shown in FIG. 46A), and wherein when the plurality of waveguide switches are programmed to perform the second function, the input waveguide switch 3833 a is used to forward wavelengths from one optical express input port 5020 b of the plurality of optical express input ports to the wavelength switch 5010 (as shown in FIG. 47A). 

What is claimed is:
 1. An optical node comprising: a first optical degree; a second optical degree; a first plurality of drop ports; a second plurality of drop ports; a first wavelength switch, used to select individual wavelengths for the first optical degree, and used to select individual wavelengths for the first plurality of drop ports; a second wavelength switch, used to select individual wavelengths for the second optical degree, and used to select individual wavelengths for the second plurality of drop ports; and a plurality of waveguide switches, operable to be set to a first mode and to a second mode, wherein when the plurality of waveguide switches are set to the first mode, the first plurality of drop ports are operable to drop wavelengths from the first optical degree and from the second optical degree, and the second plurality of drop ports are operable to drop wavelengths from the first optical degree and from the second optical degree, and wherein when the plurality of waveguide switches are set to the second mode, the first plurality of drop ports are operable to drop wavelengths only from the first optical degree, and the second plurality of drop ports are operable to drop wavelengths only from the second optical degree.
 2. The optical node of claim 1, wherein when the plurality of waveguide switches are set to the first mode, there are n number of drop ports that are operable to drop wavelengths, and wherein when the plurality of waveguide switches are set to the second mode there are m number of drop ports that are operable to drop wavelengths, wherein m is greater than n.
 3. The optical node of claim 1, wherein the first wavelength switch comprises a first plurality of wavelength equalizers, and wherein the second wavelength switch comprises a second plurality of wavelength equalizers.
 4. The optical node of claim 3, wherein each wavelength equalizer of the first plurality of wavelength equalizers comprises only one optical input and only one optical output, and wherein each wavelength equalizer of the second plurality of wavelength equalizers comprises only one optical input and only one optical output.
 5. The optical node of claim 1, wherein the plurality of waveguide switches are operable to switch wavelength division multiplexed optical signals, and wherein the plurality of waveguide switches are not operable to switch individual wavelengths within wavelength division multiplexed optical signals.
 6. The optical node of claim 1, wherein the plurality of waveguide switches includes a first waveguide switch having an optical input port, a first optical output port, and a second optical output port, wherein the first waveguide switch is operable to switch an inputted wavelength division multiplexed optical signal from the optical input port to the first optical output port, and wherein the first waveguide switch is operable to switch the inputted wavelength division multiplexed optical signal from the optical input port to the second optical output port, and wherein the first waveguide switch is not operable to simultaneously switch a first plurality of wavelengths of the inputted wavelength division multiplexed optical signal to the first optical output port and a second plurality of wavelengths of the inputted wavelength division multiplexed optical signal to the second optical output port.
 7. A wavelength switch comprising: a first optical input; a second optical input; a first optical output; a second optical output; a first optical coupler having a coupler input, a first coupler output, and a second coupler output, wherein the coupler input is connected to the first optical input; a first waveguide switch having a first switch input, a second switch input, and a switch output, wherein the first switch input is connected to the second optical input, and wherein the second switch input is connected to the first coupler output; a first wavelength equalizer having a first equalizer input and a first equalizer output, wherein the first equalizer input is connected to the second coupler output; a second wavelength equalizer having a second equalizer input and a second equalizer output, wherein the second equalizer input is connected to the switch output; a second waveguide switch having a switch input, a first switch output, and a second switch output, wherein the first equalizer output is connected to the switch input, and wherein the first switch output is connected to the first optical output; and a second optical coupler having a first coupler input, a second coupler input, and a coupler output, wherein the first coupler input is connected to the second equalizer output, and wherein the second coupler input is connected to the second switch output, and wherein the coupler output is connected to the second optical output.
 8. The wavelength switch of claim 7, wherein the first waveguide switch and the second waveguide switch are operable to be set to a first switch configuration, a second switch configuration, and a third switch configuration, wherein when set to the first switch configuration, the first waveguide switch is set so as to forward a signal from the second optical input to the second wavelength equalizer, and the second waveguide switch is set so as to forward a signal from the first wavelength equalizer to the first optical output, and wherein when set to the second switch configuration, the first waveguide switch is set so as to forward a signal from the first optical coupler to the second wavelength equalizer, and the second waveguide switch is set so as to forward the signal from the first wavelength equalizer to the first optical output, and wherein when set to the third switch configuration, the first waveguide switch is set so as to forward the signal from the second optical input to the second wavelength equalizer, and the second waveguide switch is set so as to forward the signal from the first wavelength equalizer to the second optical output.
 9. The wavelength switch of claim 7, wherein the wavelength switch is operable to be programmed to a first mode of operation, a second mode of operation, and a third mode of operation, wherein when programmed to the first mode of operation, the wavelength switch passes and blocks individual wavelengths between the first optical input and the first optical output, and the wavelength switch passes and blocks individual wavelengths between the second optical input and the second optical output, and wherein when programmed to the second mode of operation, the wavelength switch passes and blocks individual wavelengths between the first optical input and the first optical output, and the wavelength switch passes and blocks individual wavelengths between the first optical input and the second optical output, and wherein when programmed to the third mode of operation, the wavelength switch passes and blocks individual wavelengths between the first optical input and the second optical output, and the wavelength switch passes and blocks individual wavelengths between the second optical input and the second optical output.
 10. The wavelength switch of claim 7, wherein the first optical coupler is a first switchable optical coupler operable to be programmed to a first optical coupler first coupling ratio and to a first optical coupler second coupling ratio, and wherein the second optical coupler is a second switchable optical coupler operable to be programmed to a second optical coupler first coupling ratio and to a second optical coupler second coupling ratio.
 11. The wavelength switch of claim 7, wherein the first optical coupler is a first variable optical coupler operable to be programmed to a first optical coupler first coupling ratio and to a first optical coupler second coupling ratio, and wherein the second optical coupler is a second variable optical coupler operable to be programmed to a second optical coupler first coupling ratio and to a second optical coupler second coupling ratio.
 12. The wavelength switch of claim 7, wherein the first waveguide switch and the second waveguide switch are operable to be set to a first switch configuration, a second switch configuration, and a third switch configuration, wherein when set to the first switch configuration, the first wavelength equalizer passes and blocks individual wavelengths between the first optical input and the first optical output, and the second wavelength equalizer passes and blocks individual wavelengths between the second optical input and the second optical output, and wherein when set to the second switch configuration, the first wavelength equalizer passes and blocks individual wavelengths between the first optical input and the first optical output, and the second wavelength equalizer passes and blocks individual wavelengths between the first optical input and the second optical output, and wherein when set to the third switch configuration, the first wavelength equalizer passes and blocks individual wavelengths between the first optical input and the second optical output, and the second wavelength equalizer passes and blocks individual wavelengths between the second optical input and the second optical output.
 13. The wavelength switch of claim 12, wherein the first optical coupler is a first switchable optical coupler operable to be programmed to a first optical coupler first coupling ratio and to a first optical coupler second coupling ratio, and wherein the second optical coupler is a second switchable optical coupler operable to be programmed to a second optical coupler first coupling ratio and to a second optical coupler second coupling ratio, and wherein when set to the first switch configuration, the first optical coupler is set to direct its inputted light to the first wavelength equalizer and to direct none of its inputted light to the first waveguide switch, and the second optical coupler is set to direct light from the second wavelength equalizer to the second optical output and to direct no light from the second waveguide switch to the second optical output, and wherein when set to the second switch configuration, the first optical coupler is set to direct a first portion of is inputted light to the first wavelength equalizer, and to direct a second portion of is inputted light to the first waveguide switch, and the second optical coupler is set to direct light from the second wavelength equalizer to the second optical output and to direct no light from the second waveguide switch to the second optical output, and wherein when set to the third switch configuration, the first optical coupler is set to direct its inputted light to the first wavelength equalizer and to direct none of its inputted light to the first waveguide switch, and the second optical coupler is set to combine light from the first wavelength equalizer with light from the second wavelength equalizer.
 14. The wavelength switch of claim 7, wherein the first wavelength equalizer has only one optical input and only one optical output, and wherein the second wavelength equalizer has only one optical input and only one optical output.
 15. A reconfigurable optical add drop multiplexer (ROADM) of a first optical node comprising: an optical degree output port used to connect the first optical node to a second optical node; a plurality of optical express input ports, used to connect the ROADM of the first optical node to additional ROADMs within the first optical node; one or more optical drop ports; a wavelength switch, used to switch individual wavelengths within wavelength division multiplexed optical signals; and a plurality of waveguide switches that are programmable to perform a first function and a second function, wherein when the plurality of waveguide switches are programmed to perform the first function, the wavelength switch passes and blocks individual wavelengths to the optical degree output port from m number of the plurality of optical express input ports, and the wavelength switch passes and blocks individual wavelengths for n number of optical drop ports of the one or more optical drop ports, and wherein when the plurality of waveguide switches are programmed to perform the second function, the wavelength switch passes and blocks individual wavelengths to the optical degree output port from m+j number of the plurality of optical express input ports, and the wavelength switch passes and blocks individual wavelengths for n−j number of optical drop ports of the one or more optical drop ports, wherein m, n, and j are integers greater than zero, and wherein j≤n.
 16. The ROADM of claim 15, wherein the wavelength switch comprises of a plurality of wavelength equalizers.
 17. The ROADM of claim 16, wherein each wavelength equalizer of the plurality of wavelength equalizers comprises only one optical input and only one optical output.
 18. The ROADM of claim 15, further comprising a plurality of variable optical couplers to combine optical outputs of the wavelength switch.
 19. The ROADM of claim 15, wherein the plurality of waveguide switches includes an output waveguide switch, wherein when the plurality of waveguide switches are programmed to perform the first function, the output waveguide switch is used to forward one or more wavelengths from the wavelength switch to one optical drop port of the one or more optical drop ports, and wherein when the plurality of waveguide switches are programmed to perform the second function, the output waveguide switch is used to forward one or more wavelengths from the wavelength switch to the optical degree output port.
 20. The ROADM of claim 15, further comprising an optical degree input port used to connect the first optical node to the second optical node, wherein the plurality of waveguide switches includes an input waveguide switch, wherein when the plurality of waveguide switches are programmed to perform the first function, the input waveguide switch is used to forward wavelengths from the optical degree input port to the wavelength switch, and wherein when the plurality of waveguide switches are programmed to perform the second function, the input waveguide switch is used to forward wavelengths from one optical express input port of the plurality of optical express input ports to the wavelength switch. 